every single thing whatsoever follows the manner of its Being 1.' Hence, the essence of a material substance, though of itself not subject to human perception immediately in the present order of cognition, is cognizable by means of its natural operation. Accordingly, the Angelic Doctor remarks, that' When any particular operation is proper to an agent; then, by that particular operation, proof is given of the entire efficacy of the agent 2. Of course, such cognition of the essence becomes less easy, in proportion as the entity is lower in the scale of material substances and its natural operation, in consequence, less intelligible because of its captivity under matter.

PROLEGOMENON III.

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As the principiant of natural operation is one only, and the final cause in which such operation finds its consummation is likewise one; the natural operation itself, as proceeding from the one and essentially tending towards the other, is likewise specifically one. 'Natural operation,' says St. Thomas, is always terminated to some one thing; just as it proceeds from one principiant which is the Form of the natural entity 3. Since, then, operation receives specification from its term and essential unity from its principiant, it follows that the operation itself is in the same manner one.

PROLEGOMENON IV.

Natural operation, considered as complete in its term, is the ultimate perfection of the agent. Hence, Everything evidently exists for the sake of its operation; for operation is the ultimate perfection of a thing;' as it is the ultimate act of him who operates 5.

PROLEGOMENON V.

Natural operation is attributed to a twofold principiant, but

1 'Modus operandi uniuscujusque rei sequitur modum, essendi ipsius.' 10 lxxxix, I, c, init.

2 Quando aliquod particulare opus proprium est alicujus agentis, tunc per illud particulare opus probatur tota virtus agentis.' 340 xliii, 4, 3m.

3

'Operatio autem naturalis semper terminatur ad aliquid unum, sicut et procedit

ab uno principio, quod est forma rei naturalis.' 2-2a xcv, 5, c. p. m.

♦ Omnis enim res propter suam operationem esse videtur; operatio enim est ultima perfectio rei.' Cg. L. III, co 113.

5 Manifestum est autem, quod operatio est ultimus actus operantis.' I-20 iii,

2, C.

differently. It is assigned to the supposit or person; and it is assigned to the nature or essence or faculty of such essence. The former is called by the School the principium quod, or, the principiant which operates; the latter is called the principium quo, or the principiant by virtue of which the agent operates. Thus, for instance, it is Charles,-we will say,-who thinks. He is the principium quod. But it is by his intellectual nature or faculty that Charles thinks; and this is the principium quo. Hence

St. Thomas remarks that Though operation is attributed to the hypostasis' (person or supposit) 'as operating; nevertheless, it is attributed to the nature as to the principiant of operation.' This distinction will be better understood, when the fitting occasion offers for entering upon the question touching the nature of supposit and person.

DECLARATION OF THE PROPOSITION.

The doctrine evolved in the above Prolegomena renders the proof of the Enunciation easy, and obviates the necessity of elaboration. The natural operation of an entity proceeds from its specific nature. But the specific nature of an entity is determined and constituted by its substantial Form. Therefore, the natural operation of an entity proceeds from its substantial Form. If, then, there exists a diversity of Forms; there must likewise exist a diversity of operations. Accordingly, we are told by St. Thomas, that The species of the operation follows the species of the Form which is the principiant of operation 2. Wherefore, though Operation belongs to the subsisting supposit, yet according to the Form or nature from which operation receives its species. For this reason, from a diversity of Forms or natures there is a specific difference of operations 3. Since the operation follows the nature of the Form; so must likewise the potentiality which is proximate principiant of operation. Of this, too, we are certified by St. Thomas. The active potentiality of whatsoever entity,' he writes, follows its Form which is the principiant of action. Now,

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1 'Quamvis operatio attribuatur hypostasi ut operanti, tamen attribuitur naturae ut operationis principio.' Verit. Q. xx, a. 1, 2m.

2 Species operationis consequitur speciem formae quae est operationis principium.' Anima, a. 2, 7m.

3 Operari est hypostasis subsistentis, sed secundum formam et naturam a qua operatio speciem recipit. Et ideo a diversitate formarum seu naturarum est diversa species operationum. 3a xix, 1, 3m.

the Form is either the nature itself of the entity, as in simple entities; or it is that which constitutes the nature itself of the entity, as in the instance of those entities which are composed of matter and Form. Hence it is plain that the active potentiality of whatsoever entity follows the nature of that entity 1.'

COROLLARY

In the instance of every created entity, its substantial Form, either in act or actuating, is its first perfection; its complete operation, its second and ultimate perfection. For the first perfection of a thing is to be and to be, consequently, in its own specific nature; its ultimate perfection is to attain the final cause of its natural operation, since in this consists its consummation and happiness.

PROPOSITION CXC.

Diversity in the substantial Forms postulates a parallel diversity in the material cause.

DECLARATION OF THE PROPOSITION.

As we have seen, primordial matter of itself is indifferent to all Forms. Hence, though as a pure passive potentiality requiring reduction to act in order to exist, it has an essential inclination towards Form in general; nevertheless, it has no preference for one Form over another. Unless, therefore, this potentiality were in such sort modified as to direct its evolution in a definite direction, there would be no sufficient reason why it should be actuated by one Form rather than another. In fact, one modification it must receive in order to its actuation by any whatsoever Form in the constituted order. It must be portioned off, and to this end it must be modified by quantity; since no single Form exhausts the whole potentiality of matter. Hence, as the Angelic Doctor teaches and as has been elsewhere stated on his authority, quantity is the essential concomitant of the Body-Form which is, as it were, the primary determination of matter, and is virtually included in every material substantial Form. But, over and above this,

1 Potentia autem activa cujuslibet rei sequitur formam ipsius, quae est principium agendi. Forma autem vel est ipsa natura rei, sicut in simplicibus; vel est constituens ipsam rei naturam, in his scilicet quae sunt composita ex materia et forma. Unde manifestum est quod potentia activa cujuslibet rei consequitur naturam ipsius.' 3** xiii, 1, e.

matter must be inclined for the reception of each particular Form; so that the evolution of such Form may naturally follow upon the special cravings of the matter. This preparation is effected by certain dispositions given to the matter as proximately susceptive of the particular Form. In the instance of the elements which were created in the beginning, those dispositions were concreated with the creation of each element; but in natural generation these dispositions precede the eduction of the Form even in order of time. This is one reason why generation necessitates a previous corruption. By the action of the efficient cause certain qualities are introduced into the matter, which dispose the latter for the reception of the new Form, but render it proportionately disaffected towards the primitive Form; till at length the former is educed and the latter expelled. A curious illustration of this process may be seen in a fact of daily experience. If a piece of paper is thrown on a dull fire where it is not exposed to the more vehement action of a flame, it will gradually change colour and shrivel, but retain its own nature; so that it is often a considerable time before it catches fire and is transformed. The introduction of the necessary dispositions for receiving the Fire-Form in this case takes an appreciable time; because of a defect either in the efficient cause or in the due proximity of the Subject.

Now, since there is a diversity of Forms and a consequent diversity of natural operations, it follows that, in proportion to the number of different Forms, there must be a corresponding number of special dispositions in the matter; for those which are proportionate to one species must necessarily be disproportioned to another. Hence arises specific composition or specific organization according to the specific nature of the entity. Further: Since within the same species one may be more perfect than another, so that in consonance with the cosmic order there is a continuous gradation from the lowest up to those which are highest and nearest the immediately superior species, and since it is absolutely requisite that a due proportion should exist between the matter and the Form in order that the latter may be free to energize according to its natural operation; it follows that there must be a variety in the structure and organism of matter to correspond with the various species and with variations under the same species. Furthermore: The higher the Form, the more complex and perfect will be the structure of the matter. Such is the teaching of

St. Thomas, who clearly lays down the same doctrine at the end of the fourth paragraph of the fundamental passage quoted in the hundred and eighty-sixth Proposition. Matter and Form,' he there observes, could not unite to constitute any one given entity, unless there were some sort of proportion between them. But, if they must be proportioned, there must be a diversity of matter to correspond with a diversity of Form. Hence it comes to pass, that one Form postulates incomposite, and another composite, matter; and according to the diversity of Forms a difference in the composition,' or organization, of the parts is rendered necessary in accordance with the specific nature of the Form and the operation of the same.' The natural operation, indeed, has much to say to it; since the Form operates through the bodily organs.

There is one observation of the Angelic Doctor in the earlier part of the same paragraph, which requires our special notice; for without it the declaration of the present Proposition would not be complete. There is not only a proportion between matter and its Form in the constitution of each material substance; but there is a diversity in the transcendental relation of matter to different specific Forms. In some material substances the Form is wholly dependent upon the matter, even for its subsistence; while in others, the Form, though act of the body, has a subsistence of its own apart from matter. Again: Even among those Forms that are wholly dependent upon matter for their subsistence, some, -as those, for instance, of inanimate substances, are entirely immersed in matter; while others, like those of some higher orders of animals, have a certain sort of elevation above matter, as is clear from their natural operations. In the former class, as well as in the second division of the latter class, the correspondence of the matter with the Form cannot be so adequate as in the instance of those Forms which, to repeat the pregnant phrase of St. Thomas, -are wholly immersed in matter.

PROPOSITION CXCI.

From the diversity of substantial Forms there follows a diversity in the properties and accidents of the composite substance.

DECLARATION OF THE PROPOSITION.

From the specific diversity of substantial Forms there must necessarily flow a diversity in the properties of the composite