in different degrees. One man may be naturally of keener intellect and stronger will than another: the _weak_ power was what Aristotle called ?d??a?a (_impotentia_). But whether the natural powers of the same individual can _themselves_ increase or decrease in strength or intensity-and not merely the _habits_ that affect these powers-is not so clear. Operative powers are certainly perfected (or injured) by the acquisition of good (or bad) habits. In the view of those who deny a real distinction between natural operative power or faculty and substance, it is, of course, the substance itself that is so perfected (or injured).
This attribute, therefore, is _not_ found in _all_ qualities; but it is found in qualities _alone_, and not in any other category or mode of being.
How are we to conceive this variation in intensity, this growth or diminution of any quality, in a substance in which such change takes places? On this point philosophers are not agreed. By "degree of intensity"-"_intensio vel remissio __ qualitatis_"-we understand the degree (or change of degree) in which the same numerical quality affects _the same part_ or _the same power_ of its subject, thus rendering this part or power formally more or less "qualified" in some particular way.
This is clearly something quite different from the _extension_ of the same quality to different parts (or its withdrawal from different parts) of the same extended subject. In a corporeal, extended substance, there can accordingly be question of both kinds of change, _intensive_ and _extensive_; while in a simple, spiritual substance there can obviously be question only of _intensive_ change of qualities. And the fact of intensive change of qualities is an undeniable fact of experience. In what manner does it take place? Some authors conceive it as an addition or subtraction of _grades_ or _degrees_ of the same quality. Others, conceiving qualities as simple, indivisible ent.i.ties or "forms," and thence denying the possibility of distinct grades of any quality, conceive such change to take place by this simple ent.i.ty affecting its subject _more or less intimately_, becoming _more or less firmly rooted_, as it were, in its subject.(349) And they explain this more or less perfect mode of inherence in a variety of ways, all of which are grounded on certain texts of St. Thomas:(350) the quality receives a new accidental mode whereby it "communicates itself to" the subject, and "informs" the latter, more or less perfectly; or, it is educed more or less fully from the potentiality of its subject, thus qualifying the latter in the degree in which it is educed from, and rooted in, the latter.
These explanations are instructive, as ill.u.s.trating the view that the actual reality of the accidental mode of being consists in its affecting, determining, the subject in which it inheres. St.
Thomas, professing that he can attach no intelligible meaning to addition or substraction of grades,(351) teaches that the habit of charity, for example, can be increased "secundum essentiam" by "inhering more perfectly," "being more firmly rooted" in its subject; for, he says, since it is an accident, "ejus esse est inesse. Unde nihil est aliud ipsam secundum essentiam augeri, quam eam magis inesse subjecto, quod est magis eam radicari in subjecto. Augetur ergo essentialiter... ita quod magis ac magis in subjecto esse incipiat."(352) And elsewhere he concludes with the words: "Ponere igitur quod aliqua qualitas non augeatur secundum essentiam, sed augeatur secundum radicationem in subjecto vel secundum intensionem actus, est ponere contradictoria esse simul".(353)
CHAPTER XI. QUANt.i.tY, s.p.a.cE AND TIME.
82. a.n.a.lYSIS OF THE CONCEPT OF QUANt.i.tY.-A detailed study of Quant.i.ty, including s.p.a.ce and Time, and the Aristotelian categories _Ubi_, _Quando_ and _Situs_, belongs to Cosmology. Here we shall confine ourselves mainly to the exposition of certain elementary notions preparatory to such detailed study; and we shall a.s.sume the validity of the Scholastic Theory of Knowledge: that a real, material world exists independently of our minds; that it consists of material substances or bodies, animate and inanimate, endowed with the fundamental accident of quant.i.ty or extension; that these bodies possess, moreover, many other real accidents such as qualities and energies, chemical, physical and mechanical; that they are subject to real change, local, quant.i.tative, qualitative and substantial; that our concepts of s.p.a.ce and time, derived from those of extension and change, are not purely subjective or mental forms of cognition, but are objectively valid notions grounded in the reality of the corporeal universe and giving us a genuine, if inadequate, insight into the nature of this reality.
Among the characteristics recognized by physicists in all perceptible matter-divisibility, commensurability, impenetrability, pa.s.sivity or inertia, subjection to external forces or energies, external extension or volume, internal quant.i.ty or ma.s.s-there are none more fundamental than those of volume and ma.s.s, or extension and quant.i.ty.(354) Nowhere, however, do we find a better ill.u.s.tration of the fact that it is impossible to give a definition proper of any supreme category, or even a description of it by the aid of any more elementary notions, than in the attempts of philosophers to describe _Quant.i.ty_. When, for instance, we describe _external_, _actual_, _local_, or _spatial extension_ as _that accident of a corporeal substance or body in virtue of which the latter so exists that it has parts outside parts in s.p.a.ce_, we have to admit at once that the notions expressed by the terms "parts," "outside" and "s.p.a.ce" are no simpler than the notion of extension itself: in fact our notions of "place" (_locus_) and "s.p.a.ce" (_spatium_) are derived from, and presuppose, that of extension. This, however, is no serious disadvantage; for the description, such as it is, indicates what we mean by the terms "local, spatial, external, actual extension," and declares this latter to be an accident of corporeal substances.
Extension, as it is actually in the concrete body, affected by a variety of sensible qualities, is called _physical_ extension; regarded in the abstract, apart from these qualities, it is called _geometrical_ or _mathematical_ extension: _trina dimensio_, or extension in three dimensions, length, breadth and depth. If we abstract from one of these we have extension in _two_ dimensions, _superficial_ extension; if we abstract from _two_, we have extension in _one_ dimension, _linear_ extension; and if we abstract from all three we have the extreme _limiting concept_ of the _mathematical point_. Of these four abstract mathematical concepts, "point," "line," "surface," and "volume," each expresses the _mathematical limitation_ of the succeeding one.
We cannot conceive a body existing by having parts outside parts in s.p.a.ce, each part occupying exclusively a place appropriated to itself, unless we conceive the body, the corporeal _substance_, as having already a plurality of _really distinct_ or _distinguishable_ parts _in itself_, and abstracting from all relation to s.p.a.ce. The _substance_ must be conceived as having a plurality of really distinct or distinguishable _integral_ parts of itself, before these parts can be conceived as existing _outside_ one another, each in its own place. And the property in virtue of which the corporeal substance has in itself this plurality of distinct integral parts, whereby it is _capable_ of occupying s.p.a.ce, and of being impenetrable, divisible, measurable, etc., is called _internal_, _radical_, _potential quant.i.ty_ or _extension_.(355)
The corporeal substance itself is, of course, _essentially_ composite, essentially divisible into two _essential_ const.i.tutive principles, the pa.s.sive, determinable, or material principle (_materia prima_), and the specifying, determining, formative principle (_forma substantialis_). Then we conceive this essentially composite substance as necessarily endowed with the _property_ of _internal quant.i.ty_ whereby it is composite in another order: composed of, and divisible into, really distinct _integral_ parts, each of which is, of course, essentially composite like the whole itself.(356) Finally we conceive that the corporeal substance, endowed with this property, has also, as a connatural but really distinct and absolutely separable effect of the latter, the accidental mode of being, called external or local extension, in virtue of which it actually occupies s.p.a.ce, and thus becomes the subject of all those qualities whereby it is perceptible to our senses.
We have next to inquire into the relations between these three distinct objective concepts, corporeal substance, internal quant.i.ty, and local or external extension.
83. CORPOREAL SUBSTANCE, QUANt.i.tY AND EXTENSION.-The corporeal substance is an essentially composite substance, resulting from the union of two distinct essential const.i.tutive principles. It exists in itself and is the ultimate subject of all the determinations whereby it reveals itself to our senses. Its actual extension in s.p.a.ce is a fundamental mode or determination of its reality, but it is a mode which is distinct from the reality itself of the corporeal substance. Aristotle regarded the distinction as real. In his _Metaphysics_ he declares that the three dimensions of bodies are quant.i.ties, not substances, that quant.i.ty is not a substance, whereas that in which it ultimately inheres is a substance;(357) in his _Physics_ he says that substance is of itself indivisible and is made divisible by its quant.i.ty or extension;(358) in his _De Anima_(359) he observes that [external] quant.i.ty is directly perceptible by the senses (_sensibile_ per se) while substance is only indirectly perceptible (_sensibile_ per accidens):(360) from which it is inferred that substance and extension cannot be really identical. Again, St. Thomas argues that a corporeal substance as such, and so far as its essence is concerned, is indifferent to greater or less extension in s.p.a.ce, that the whole nature or substance of a man, for instance, is indifferent to, and independent of, his particular size at any point of time, that while he grows from childhood to manhood it is his external quant.i.ty that changes, but not his humanity, his human essence, nature, or substance.(361)
Considerations such as these, though they do not indeed amount to cogent proofs of a real distinction between spatial extension and corporeal substance, should make any serious philosopher hesitate to identify these absolutely, as Descartes and his followers did when they declared the essence of corporeal substance to consist in three dimensions of spatial extension. Even looking at the matter from the point of view of natural reason alone, and apart altogether from any light that may be thrown upon it for the Christian philosopher by Divine Revelation, it is only the superficial thinker who will conclude that because extension-which reveals to his intellect through the medium of external sense perception the presence of a corporeal substance-is naturally inseparable from the latter, therefore it is really and absolutely identical with this latter.
The philosopher who remembers how little is known for certain about the ultimate, essential const.i.tution of bodies or corporeal substances, will be slow to conclude that the spatially extended mode of their being enters into the const.i.tution of their essence, and is not rather an accidental determination whereby these substances have their integral parts dispersed or extended in s.p.a.ce and thus revealed to the human intellect through sense perception.
And if he be a Christian philosopher he will naturally inquire whether any truth of the Christian Revelation will help indirectly to determine the question. Descartes and his followers were Christian philosophers; and hence it was all the more rash and imprudent of them, in spite of what they knew concerning the Blessed Eucharist, to identify the corporeal substance with its spatial extension. They knew that by transubstantiation the bread and wine are changed _substantially_ into the Body and Blood of Christ. But all the _appearances_ or _phenomena_ of bread and wine remain after transubstantiation, the Eucharistic _species_ as they are called, the taste, colour, form, etc., in a word, all the sensible qualities of these substances, including the _extension_ in which they immediately inhere. From the revealed truth that the _substances_ disappear, and from the manifest fact that all their _accidents_ remain, Christian philosophers and theologians have rightly drawn the sufficiently obvious inference that the spatially extended quant.i.ty, which immediately supports all the other sensible qualities, must be itself an _absolute_ accident not only _really distinct_, but by the absolute power of G.o.d _really separable_, from its _connatural substance_, the bread and the wine respectively; and that this extended quant.i.ty remains in this state of actual separation miraculously supported by the direct influence of the Divine Omnipotence. And while Christian philosophers who hold this view can defend it from all charges of inconsistency, unreasonableness and impossibility, Descartes and his followers can defend their particular view only by the admission that in the case of the consecrated Eucharist our senses are deceived. In this view, while no accidents of the bread and wine remain objectively, G.o.d Himself produces directly in our minds the subjective, mental states which the bread and wine produced before consecration.(362) This gratuitous aspersion is cast on the trustworthiness of sense perception, simply on account of the preconceived theory identifying the corporeal substance with its extension. According to the common view, on the other hand, the senses are not really deceived. That to which they testify is really there, _viz._ the whole collection of natural accidents of bread and wine. It is not the function of the senses, but of the intellect, to testify to the presence of the substance.
Of course the unbeliever looking at the consecrated species, or the believer who looks at them not knowing that they have been consecrated, thinks that the substance of bread and the substance of wine are there. Each is deceived intellectually, the one by his unbelief of a truth, the other by his ignorance of a fact. If both knew of the fact of consecration, and if the former believed in the effect of it, neither would be deceived.(363)
While the Cartesian view is thus open to such serious objections, the only plausible difficulty against the traditional view is that of conceiving how the reality of a merely accidental mode of being, such as extension, can be sustained in the actual order of things apart from its connatural substance, and yet not become itself _eo ipso_ a substance. Needless to say we have no _positive_ conception of the manner in which the Divine Omnipotence thus sustains extension; but since this latter, being an absolute accident, and not a mere modal determination of the substance, has a reality of its own, the miraculous persistence of this reality cannot be shown to be impossible. Nor is it, in this separated condition, itself a substance, for it still retains its natural apt.i.tude for inherence in its connatural substance; and this _apt.i.tude_ alone, not _actual_ inherence, is of its essence as an accident (65): retaining this natural apt.i.tude it cannot possibly become a substance, it cannot be identified with the _substantial_ mode of being which has essentially the very opposite apt.i.tude, that of _existing in itself_.
External extension, then, is an absolute accident, really distinct from the corporeal substance, and naturally though not absolutely inseparable from the latter. It is the natural concomitant or consequence of the _internal quant.i.ty_ whereby the corporeal substance has in itself a plurality of distinct integral parts. This _internal quant.i.ty_ itself is either an aspect of the corporeal substance itself, only virtually distinct from the latter, or else in the strict sense a _property_, absolutely inseparable, if really distinct, from the substance. Natural experience furnishes no example of a corporeal substance actually existing devoid of internal quant.i.ty or internal distinction of integral parts.(364) But scholastic philosophers are not agreed as to whether the corporeal substance is itself and by its own essence a manifold of really distinct integral parts (in which case internal quant.i.ty would be merely the aspect under which the essence is thus regarded as an integral whole const.i.tuted by a plurality of distinct integral parts; while, looked at as an essence, it would be an essential whole const.i.tuted by the union of two essential parts or principles)-or whether it is formally const.i.tuted an integral whole, not by its essence (which makes it only an essential whole, an essentially composite substance), but by a property really distinct, though necessarily flowing, from this essence, _viz._ internal quant.i.ty. According to the former view the material principle (_materia prima_) of the composite corporeal substance is such that the essence resulting from its union with the formative principle (_forma substantialis_) is necessarily an integral whole with distinguishable integral parts, each of which naturally demands the spatially extended mode of being which external extension _de facto_ confers upon it.
According to the latter view, which is that of St. Thomas and his followers generally, the corporeal substance as such has no mode of composition other than _essential_ composition: it is not of itself an _integral_ whole, compounded of distinct or distinguishable integral parts (each of which would be, like the whole, essentially composite): of itself it is _indivisible_ into integral parts: it is, therefore, in this order of being, simple and not composite. It has, no doubt, by reason of its material principle, an absolutely necessary exigence for divisibility into distinct integral parts, for integral composition in other words. But this actual integral composition, this actual divisibility, is the formal effect of a property really distinct from the substantial essence itself; and this property is internal quant.i.ty: the connatural, but absolutely separable, complement of this internal quant.i.ty being, as in the other view, local or spatial extension.
In both views external extension is an absolute accident of the corporeal substance; and in the Thomist view internal quant.i.ty would also appear to be an absolute accident, and not a mere mode.
It is instructive to reflect how far this scholastic doctrine removes us from the Cartesian view which sets up an absolute ant.i.thesis between mind or spirit, and matter or body, placing the essence of the former in _thought_ and that of the latter in _extension_. According to the scholastic view the spiritual substance is an immaterial "actuality" or "form"; it is _essentially simple_, and not like a corporeal substance an _essentially composite_ substance resulting from the union of a formative principle or "form" with a pa.s.sive, determinable, material principle. And since it is the material principle that demands the property of internal quant.i.ty and the accident of external extension, whereby the corporeal substance becomes an integral whole with its parts extended in s.p.a.ce, it follows that the spiritual substance, having no material principle in its const.i.tution, is not only _essentially_ simple-to the exclusion of distinct principles of its essence,-but is also and as a consequence _integrally_ simple, to the exclusion of distinct integral parts, and of the extended or characteristically corporeal mode of occupying s.p.a.ce. So far there is contrast between the two great substantial modes of finite being, matter and spirit; but the contrast is by no means an absolute ant.i.thesis. For if we look at the essence alone of the corporeal substance it is not _of itself_ actually extended in s.p.a.ce: in the Thomist view it is not even of itself divisible into distinct integral parts. It differs from spirit in this that while the latter is essentially simple the former is essentially composite and has by reason of this compositeness a natural apt.i.tude for divisibility into parts and for the extension of these parts in s.p.a.ce, an apt.i.tude which spirit does not possess. But the corporeal substance _may_ exist without actual extension, and consequently without any of those other attributes such as impenetrability, solidity, colour, etc., through which it is perceptible to our senses. In this condition, how does it differ from spirit? In being essentially composite, and in being perhaps endowed with distinguishable integral parts.(365) But in this condition the essential mode of its being has a relation to s.p.a.ce which closely resembles the mode in which spirit exists in s.p.a.ce: it is related to s.p.a.ce somewhat in the manner in which the soul is in the s.p.a.ce occupied by the body-whole in the whole of this s.p.a.ce and whole in every a.s.signable portion of this s.p.a.ce. So that after all, different as matter and spirit undoubtedly are, the difference between them is by no means that sort of Cartesian chasm which human thought must for ever fail to bridge.
By virtue of its external extension the corporeal substance exists by having distinguishable parts outside parts in s.p.a.ce. We can conceive any perceptible volume of matter as being _perfectly continuous_, if it has no _actual_ limits or _actual_ distinction of parts within itself, but is _one_ individual being _completely filling_ the whole s.p.a.ce within its outer surface; or _imperfectly continuous_, if while being one and undivided it has within its volume pores or interstices, whether these be empty or filled with some other sort of matter; or as made up of _contiguous_ integral parts if each or these is really distinct and actually divided from every other, while each actually touches with its outer limits the adjacent limits of the parts lying next to it, so that all the internal parts or limits are co-terminous; or as made up of separate, _discrete_ or distant parts no one of which actually touches any other.
It is clear that there must be, in any actually extended volume of matter, _ultimate_ parts which are really _continuous_-unless we are to hold, with dynamists, that our perception of extension is produced in our minds by the action of extramental points or centres of force which are themselves _simple_ or _unextended_. But the physical phenomena of contraction, expansion, absorption, undulatory and vibratory motions accompanying our sensations of light, heat and sound, as well as many other physical phenomena, all point to the fact that volumes of matter which are _apparently_ continuous are really porous: the molecular structure of perceptible matter is an accepted physical theory; and scientists also universally accept as a working hypothesis the existence of an imperceptible material medium pervading and filling all real s.p.a.ce, though there is no agreement as to the properties with which they suppose this hypothetical medium, the "ether," to be endowed.
Again, as regards the _divisibility_ of extended matter, it is obvious that if we conceive extension in three dimensions _geometrically_, _mathematically_ or _in the abstract_, any such volume or extension is _indefinitely divisible_ in thought. But if we inquire how far any concrete, actually existing volume of matter is divisible, we know in the first place that we cannot divide the body of any actual organic living thing indefinitely without destroying its life, and so its specific character. Nor can we carry on the division of inorganic matter indefinitely for want of sufficiently delicate dividing instruments. But apart from this the science of chemistry points to the fact that every inorganic chemical compound has an ultimate individual unit, the chemical molecule, which we cannot sub-divide without destroying the specific nature of the compound by resolving it into its elements or into less complex compounds. Furthermore, each "elementary" or "chemically simple"
body-such as gold, oxygen, carbon, etc.-seems resolvable into units called "atoms," which appear to be ultimate _individual_ units in the sense that if their ma.s.s _can_ be subdivided (as appears possible from researches that have originated in the discovery of radium) the subdivisions are specifically different kinds of matter from that of the atom so divided.
In the inorganic world the perceptible ma.s.s of matter is certainly not an _individual_ being, a _unum per se_, but only a collection of individual atoms or molecules, a _unum per accidens_. Whether the molecule or the atom of the chemically elementary body is the "individual," cannot be determined with any degree of cert.i.tude. It would appear, however, that every specifically distinct type of inorganic matter, whether compound or elementary, requires for its existence a certain minimal volume, by the sub-division of which the type is substantially changed; and this is manifestly true of organic or living matter: so that matter _as it naturally exists_ would appear not to be indefinitely divisible.
If in a chemically h.o.m.ogeneous ma.s.s of _inorganic_ matter (such as carbon or water) the chemical molecule be regarded as the "individual," this cannot be the case in any _organic_, _living thing_, for whatever matter is a.s.similated into the living substance of such a being _eo ipso_ undergoes substantial change whereby it loses the nature it had and becomes a const.i.tuent of the living individual. The _substantial_, "_individual_" unity of the organic living being seems to be compatible not merely with qualitative (structural and functional) heterogeneity of parts, but also with (perhaps even _complete_) spatial separateness of these parts. If the structure of the living body is really "molecular," _i.e._ if it has _distances_ between its ultimate integral units, so that these are not in spatial contact, then the fact that the formative, vital principle (_forma substantialis_, _anima_) unifies this material manifold, and const.i.tutes it an "individual" by actualizing and vitalizing each and all of the material units, spatially separate as they are,-this fact will help us to realize that the _formative principle_ of the composite corporeal substance has not _of itself_ the _spatial_, _extended_ mode of being, but that the substance derives the latter from its material principle (_materia prima_).
84. PLACE AND s.p.a.cE.-From the concept of the volume or actual extension of a body we pa.s.s immediately to that of the "place" (_locus_) which it occupies. We may distinguish between the _internal_ and the _external_ place of a body. By the former we understand _the outer (convex) surface of the body itself, regarded as a receptacle containing the volume of the body_. If, therefore, there were only one body in existence it would have its own internal place: this is independent of other bodies. Not so, however, the external place; for by the external place of a body we mean _the immediately surrounding (concave) surface_, formed by the bodies which circ.u.mscribe the body in question, and _considered formally as an immovable container of this body_. This is a free rendering of Aristotle"s definition: _Place is the first (or immediate) immovable surface (or limit) of that which contains a body_: _prima immobilis superficies ejus quod continet_.(366) If a hollow sphere were filled with water, the inner or concave surface of the sphere would be the "external place" of the water. Not, however, this surface considered materially, but _formally as a surface_, so that if the sphere could be removed, and another instantaneously subst.i.tuted for it, the water would still be contained within the same _formal_ surface; its _locus externus_ would remain the same. And, again, it is the containing surface considered as _immovable_ or as circ.u.mscribing that definite portion of s.p.a.ce, that const.i.tutes the _locus externus_ or "external place" of the located body: so that if the sphere with the water were moved the latter would thereby obtain a new external location, for though the containing surface be still materially and formally the same, it is no longer the same _as a locating_ surface, seeing that it now marks off a portion of s.p.a.ce different from that marked off by it before it was moved.
Aristotle"s definition defines what is known as the _proper_ external place of a body. From this we distinguish the _common_ external place or location of a body: understanding by the latter, or "locus _communis_,"
the whole collection of spatial relations of the body in question to all the bodies in its immediate neighbourhood. It is by indicating these relations, or some of them, that we a.s.sign the Aristotelian category, or extrinsic denomination, _Ubi_.(367)
Regarded ontologically, the internal place of a body is an absolute accident: it is the accident which gives the latter concrete volume or external extension, and it is not really distinct from the latter. The external place of a body includes in addition the spatial relations of the latter to other bodies, relations grounded in the volumes of those bodies.
It is by reason of these spatial relations with certain bodies, that a being is said to be "present" in a certain place. A corporeal extended substance is said to occupy s.p.a.ce _circ.u.mscriptive_, or by having parts outside parts in the place it occupies. A finite or created spiritual substance is said to occupy s.p.a.ce _definitive_ inasmuch as it can naturally exercise its influence only within certain more or less extended spatial limits: as the human soul does within the confines of the body.(368) The Infinite Being is said to occupy s.p.a.ce _repletive_.
The actual presence of G.o.d in all real s.p.a.ce, conserving in its existence all created, contingent reality, is called the Divine _Ubiquity_. The perfection whereby G.o.d can be present in other worlds and other s.p.a.ces which He may actualize is called the Divine _Immensity_.
The local presence of a finite being to other finite beings is itself a positive perfection-based on its actual extension if it be an extended corporeal substance, or on its power of operating within a certain s.p.a.ce if it be a spiritual substance. The fact that in the case of a finite being this local presence is itself limited, is at once a corollary and an index of the finiteness of the being in question. Only the Infinite Being is omnipresent or ubiquitous. But every finite being, whether corporeal or spiritual, from the very fact that it exists at all, must exist somewhere or have some _locus internus_, and it must have some local presence if there are other corporeal, extended beings in existence. Thus the _local presence_ of a being is a (finite) perfection which seems to be grounded in the very nature itself of the creature.(369)
From the concept of _place_ we pa.s.s naturally to the more complex and abstract notion of _s.p.a.ce_. It is, of course, by cognitive processes, both sentient and intellectual, that we come into possession of the abstract concept of s.p.a.ce. These processes are subjective in the sense that they are processes of the individual"s mental faculties. Distinguishing between the processes and the object or content which is brought into consciousness, or put in presence of the mind, by means of them; and a.s.suming that this object or content is not a _mere_ form or groove of our cognitive activity, not a _mere_ antecedent condition requisite on the mental side for the conscious exercise of this activity on its data, but that on the contrary it is, or involves, an objective, extramental reality apprehended by the mind,-we go on to inquire in what this objective reality consists. In approaching the question we must first note that what is true of every abstract and universal concept is true of the concept of s.p.a.ce, _viz._ that the _abstractness_ and _universality_ ("_intentio universalitatis_") of real being, as apprehended by the intellect, are modes or forms of thought, _entia rationis_, logical conditions and relations which are created by thought, and which exist only in and for thought; while the reality itself is the object apprehended in these modes and under these conditions: _Universale est formaliter in mente et fundamentaliter in re_. Now through the concept of s.p.a.ce we apprehend a reality. Our concept of real s.p.a.ce has for its object an actual reality.
What is this reality? If s.p.a.ce is real, in what does its reality consist?
We answer that the reality which we apprehend through this concept is _the total amount of the actual extension or magnitude of all created and coexisting bodies_; not, however, this total magnitude considered absolutely and in itself, but _as endowed with real and mutual relations of all its parts to one another_,(370) relations which are apprehended by us as distances, linear, superficial, and voluminal.
Such, then, is the reality corresponding to our concept of real and actual s.p.a.ce. But no sooner have we reached this concept than we may look at its object in the abstract, remove mentally all limits from it, and conceive all extended bodies as actually non-existent. What is the result? The result is that we have now present to our minds the _possibility_ of the existence of extended bodies, and a concomitant imagination image (which memory will not allow us to banish from consciousness) of a vast and boundless emptiness, an indefinite and unmeasurable vacuum in which bodies were or may be. The intellectual concept is now not a concept of any _actual_ object, but of a mere _possibility_: the possibility of a corporeal, extended universe. This is the concept of what we call _ideal_ or _possible s.p.a.ce_; and like the concept of any other possible reality it is derived by us from our experience of actual reality,-in this case from our experience of extended bodies as actually existing. The corporeal universe has not existed from all eternity, but it was possible from all eternity. When we think of that possibility as antecedent to all creation, we are thinking of bodies, and of their extension, as possible; and the concept of their total extension as possible is the concept of ideal or possible s.p.a.ce. This concept is, through a psychological necessity, accompanied by an imagination image of what we call _imaginary s.p.a.ce_: the unlimited vacuity which preceded corporeal creation, which would still persist were the latter totally annihilated, which reaches out indefinitely beyond its actual limits, which imagination pictures for us as a receptacle in which bodies may exist but which all the time our reason a.s.sures us is actually nothing, being really only the known possibility of corporeal creatures. This familiar notion of an empty receptacle for bodies is what we have in mind when we think of bodies as existing "_in_ s.p.a.ce". Hence we say that s.p.a.ce, as conceived by the human mind, is not a mere subjective form of cognition, a mere _ens rationis_, inasmuch as our concept has a foundation in reality, _viz._ the actual extension of all existing bodies; nor is it on the other hand simply a real ent.i.ty, because this actual extension of bodies does not really exist in the manner in which we apprehend it under the abstract concept of s.p.a.ce, as a mere possibility, or empty receptacle, of bodies. s.p.a.ce is therefore an _ens rationis c.u.m fundamento in re_.
A great variety of interesting but abstruse questions arise from the consideration of s.p.a.ce; but they belong properly to Cosmology and Natural Theology. For example: Is real s.p.a.ce actually infinite in magnitude, or finite? In other words, besides the whole solar system-which is in reality merely one star _plus_ its planets and their satellites,-is there in existence an actually infinite mult.i.tude of such stellar worlds? It is not likely that this can ever be determined empirically. Many philosophers maintain that the question must be answered in the negative, inasmuch as an actually infinite mult.i.tude is _impossible_. Others, however, deny that the impossibility of an actually infinite mult.i.tude can be proved.(371) Again, within the limits of the actual corporeal universe, are there really _vacant_ s.p.a.ces, or is all s.p.a.ce within these limits actually (or even necessarily) filled with an all-pervading ether or corporeal medium of some sort? How would local motion be possible if all s.p.a.ce were full of impenetrable matter? How would the real interaction of distant bodies on one another be possible if there were only vacant s.p.a.ce between them?
Is the _real_ volume or extension of a corporeal substance (as distinct from its _apparent_ volume, which is supposed to include interstices, or s.p.a.ces not filled with that body) actually or necessarily unchangeable? Or is the internal quant.i.ty of a body actually or necessarily unchangeable? Can more than one individual corporeal substance simultaneously occupy exactly the same s.p.a.ce?
(This is not possible naturally, for impenetrability is a natural consequence of local extension; but it is possible miraculously-if all the bodies, or all except one, be miraculously deprived of local or spatial extension.) Can the same individual body be present at the same time in totally different and distant places?
(Not naturally, of course; but how it can happen even miraculously is a more difficult question than the preceding one. It is in virtue of its actual or local extension that a body is present sensibly in a definite place. Deprived miraculously of this extension it can be simultaneously in several places, as our Blessed Lord"s Body is in the Eucharist. But if a body has its natural local extension at one definite place, does this extension so confine its presence to this place that it cannot be simultaneously present-miraculously, and without its local extension-at other places? The most we can say is that the absolute impossibility of this is neither self-evident nor capable of cogent proof. The Body of our Lord has its natural local extension in heaven-for heaven, which will be the abode of the glorified bodies of the blessed after the general resurrection, must be not merely a state or condition, but a place-and at the same time it is sacramentally present in many places on earth.)
85. TIME: ITS APPREHENSION AND MEASUREMENT.-If the concept of s.p.a.ce is difficult to a.n.a.lyse, and gives rise to some practically insoluble problems, this is still more true of the concept of time. "What, then, is time?" exclaims St. Augustine in his _Confessions_.(372) "If no one asks me, I know; but if I am asked to explain it, then I do not know!" We reach the notion of s.p.a.ce through our external perception of _extension_ by the senses of sight and touch. So also we derive the notion of time from our perception of _motion_ or _change_, and mainly from our consciousness of change and succession in our own conscious states. The concept of time involves immediately two other concepts, that of _duration_, and that of _succession_. Duration, or continuance in existence, is of two kinds, _permanent_ and _successive_. Permanent duration is the duration of an _immutable_ being, formally and in so far as it is immutable. Successive duration is the continued existence or duration of a being that is _subject_ to change, formally and in so far as it is mutable. Now real change involves a continuous _succession_ of real states, it is a continuous _process_ or _fieri_; and it is the duration of a being subject to such change that we call _time_ or _temporal duration_. Had we no consciousness of change, or succession of states, we could have no notion of time; though we might have a notion of unchanging duration if _per impossibile_ our cognitive activity were itself devoid of any succession of conscious states and had for its object only unchanging reality. But since our cognitive activity is _de facto_ successive we can apprehend permanent or unchanging duration, not as it is in itself, but only after the a.n.a.logy of successive or temporal duration (86). The continuous series of _successive states involved in change_ is, therefore, the real and objective content of our notion of time; just as the _co-existing_ total of _extension_ forms the content of our notion of s.p.a.ce. The concept of s.p.a.ce is the concept of something static; that of time is the concept of something kinetic. Time is the continuity of change: where there is change there is time; without change time would be inconceivable. Change involves succession, and succession involves the temporal elements of "before" and "after," separated by the indivisible limiting factor called the "now" or "present instant". The "past" and the "future" are the two _parts_ of time, while the "present instant" is not a part of time, but a _point of demarcation_ at which the future flows into the past. Change is a reality; it is a real mode of the existence of mutable things; but neither the immediately past state, nor the immediately future state of a changing reality, are actual at the present instant: it is only to the permanent, abiding mind, apprehending real change, and endowed with memory and expectation, that the past and the future are actually (and, of course, only _ideally_, not _really_) present. And it is only by holding past and future in present consciousness, by distinguishing mentally between them, by counting or measuring the continuous flow of successive states from future to past, through the present instant, that the mind comes into possession of the concept of time.(373) The mind thus apprehends time as the measure of the continuous flow of successive states in things subject to change. As thus apprehended, time is not merely the reality of change: it is the successive continuity or duration of change considered as a measure of change. It is that within which all changes are conceived to happen: just as s.p.a.ce is conceived as that within which all extended things are conceived to exist. We have said that without real change or motion there could be no time. We can now add that without a mind to apprehend and measure this motion there could be no time. As St. Thomas declares, following Aristotle: _Si non esset anima non esset tempus_.(374) For time, as apprehended by means of our abstract and universal concept, is not simply a reality, but a reality endowed with logical relations, or, in other words, a logical ent.i.ty grounded in reality, an _ens rationis c.u.m fundamento in re_.
This brings us to Aristotle"s cla.s.sic definition,(375) which is at once pithy and pregnant: ???t? ??? ?st?? ? ??????, ?????? ????se?? ?at? t?
p??te??? ?a? ?ste???: _Tempus est numerus motus secundum prius et posterius_: Time is the measure of motion or change by what we conceive as _before_ and _after_, or _future_ and _past_, in its process. Every change involves its own intrinsic flow of states from future to past. It is by mentally distinguishing these states, and by thus computing, counting, numbering, the continuous flow or change, that we derive from the latter the notion of time.(376) If, then, we consider all created things, all things subject to change, we shall realize that real time commenced with the creation of the first of them and will continue as long as they (or any of them) continue to exist. We thus arrive at a conception of time in general, a.n.a.logous to that of s.p.a.ce: _the whole continuous series of successions, in changing things, from future to past, regarded as that in which these changes occur, and which is the measure of them_.
Here, too, as in the case of s.p.a.ce, we can distinguish _real time_, which is the total duration of actual changes, from _ideal or imaginary time_ which is the conceived and imagined duration of merely possible changes.
But a more important distinction is that between _intrinsic_ or _internal time_, or the duration of any concrete mutable reality considered in itself, and _extrinsic_ or _external time_, which is some other extrinsic temporal duration with which we compare, and by which we may measure, the former duration. Every change or motion has its own internal time; and this is what we have been so far endeavouring to a.n.a.lyse. If two men start at the same instant to walk in the same direction, and if one walk three miles and the other four, while the hands of a watch mark the lapse of an hour, the _external time_ of each walk will be the same, will coincide with one and the same motion of the hands of the watch used as a measure.
But the internal time of the four-mile walk will be greater than that of the three-mile walk. The former will be a greater amount of change than the latter; and therefore its internal time, estimated by this amount absolutely, will be greater than that of the latter estimated by its amount absolutely.(377) The greater the amount of a change the greater the internal time-duration or series of successive states which measures this change absolutely.(378)