Leibniz solved the problem by reducing extension to the attribute of thought through a system of thinking substances in Godâs intellect. The experience in these simple substances, or monads, is comprehended in a system of perspectives in Godâs nature as conceived through thought. The same experience is also conceived through extension as the appearance of the external world, but this is ultimately explicable through the same attribute, as a result of Godâs pre-established harmony of the experience in finite perspectives. Spinoza developed the same system in many respects, in as much as according to the absolute idealist reading the system of finite and infinite perspectives in substance is like the system of monads. But Leibnizâs objection to Spinozaâs main proof of the uniqueness of substance in the Ethics suggests that the difference in the ways the whole of reality appears as conceived through diverse attributes entails a numerical diversity of substances. Spinoza never published his response. Although he might have discussed the objection with Leibniz when they met before Spinozaâs death in 1677, the objection appeared in Leibnizâs commentary on the Ethics of 1678. Nevertheless, a possible response is discussed in the second section of this chapter.
The uniqueness of substance and Descartesâ mind-body dualism
The development of Descartesâ system in the direction of Spinozaâs monism contains a significant advantage. Watson diagnoses the âbreakdown of Cartesian metaphysicsâ as in part due to its inability to resolve the problem Spinoza saw in Descartesâ mind-body dualism.1 Watson finds that none of the various attempts made by Descartes or others to resolve the issue could be made to work on the basis of a dualistic ontology, as every attempt to bridge the gap implies that the mind is after all body or that the body is after all the mind in a way that Spinoza would have seen as altogether predictable. Spinozaâs solution to the problem is the uniqueness of substance; it represents the advantage of Spinozaâs system over that of Descartes. Whether the solution brings with it other types of difficulty, a monistic ontology cannot be eliminated from the system without also eliminating any advantage it has over dualistic or pluralistic alternatives.
Spinoza and Descartes were in agreement on many points. They agreed in fundamental respects about the meaning of the technical terms of 17th-century rationalism, substance, attribute and mode. âBy substanceâ wrote Descartes, âwe understand nothing other than a thing which exists in such a way as to depend on no other thing for its existence. And there is only one substance which can be understood to depend on no other thing whatsoever, namely Godâ (AT 8.1/24).2 Spinoza believed that substance is the cause of itself, or that, in another manner of speaking, it depends for its existence on itself alone (ElP7Dem). Spinoza also believed that there is, if substance is understood in the strict sense of a wholly independent being, only one substance and that this substance is God (E1P14). Thus, Spinoza and Descartes were very much in agreement in their use of substance in as much as they each used the term in its primary sense, as entailing, or designating, an ontologically independent being. Spinoza reinterpreted the entities to which Descartes applied the term imprecisely, such as individual finite minds and bodies. Spinoza considered these finite modes of the one substance. Such modes of substance are not independent in the ways substance is, as it alone is in and conceived through itself (E1D3; see also E1D5); rather, a finite mind and its body are only independent of each other in as much as they are one part of the reality of substance independently conceived through their respective attributes.
Attribute is also used in very much the same way in the writings of Spinoza and in those of Descartes. Attribute was defined by Descartes in these terms: âeach substance has one principal property which constitutes its nature and essenceâ (AT 8.1/25). As in Spinozaâs E1D4 definition of the term attribute â âBy attribute I understand what the intellect perceives of a substance as constituting its essenceâ â the essence of a substance is also, according to Descartesâ definition, something perceived by the intellect. This is again evident from the conclusion Descartes drew from the analogy developed in the Meditations of the wax and extended, or corporeal, substance: âthe perception I have of it is a case not of vision or touch or imagination ⌠but of purely mental scrutinyâ (AT 7/31). The changing qualities, or affections, of the wax or any extended substance as perceived through the senses or as portrayed as such in the imagination are unessential to the nature that remains throughout. The nature that remains a stable reference point throughout these changes is the attribute of a substance, and this attribute is the ground for developing a systematic understanding of this substanceâs modes.
Spinoza also regarded the modes of substance as modifications of something remaining stable throughout (E1D5). This is evident from the conclusion Spinoza drew from the analogy of substance and water: âwater, insofar as it is water, is generated and corrupted, but insofar as it is substance, it is neither generated nor corruptedâ (ElP15Schol). This is because substance is the stable point of reference by means of which one understands the appearances and changes of things; a substance, as it is in itself, is its essential attribute.
The relation between substance and its modes is also very much the same for Spinoza and for Descartes, as the latter thought it wise to allow that
By mode ⌠we understand exactly the same as what is ⌠meant by an attribute or quality. But we employ the term mode when we are thinking of substance as being affected or modified; when the modification enables the substance to be designated as a substance of such and such a kind, we use the term quality; and finally, when we are simply thinking in a more general way of what is in a substance, we use the term attribute. (AT 8.1/26)
Both Spinoza and Descartes wanted to emphasis that an attribute is not the quality of the species distinguishing it from other individuals bearing the features of a genus. Cartesian attributes do not merely classify the reality of a substance but can be used to derive its modes; moreover, as a mode inheres in substance as understood through its attribute, modes are dependent beings for both Spinoza and Descartes.
The modes characteristic of thought and extension, as described in Spinozaâs God, Man, and His Well-being, are also quite like those Descartes mentioned. The principal modes of thought for Descartes are those of a âthing that thinksâ, or of a substance that âdoubts, understands, affirms, denies, is willing, is unwilling, and also imagines and has sensory perceptionsâ (AT 7/28). The modes of extension are for Descartes the modifications of body, or extended substance, and its principal modifications are âlength, breadth and depthâ (AT 8.1/42). Spinoza also suggested that we may call the modes of extension âlength, breadth, and depthâ. Spinoza was also very much a Cartesian in his use of idea to refer to any mode of thought, as suggested by his definition of the term in the Ethics (E2D3) and his inclusion of âwilling, sensing, understanding, loving, ect.â, among the modes of thinking substance.3
Whereas Descartesâ metaphysics stresses the concept of matter as the independent bearer of form, Spinoza emphasized the one of Plotinus, with the reality of matter emanating from the one through the order of intelligence and the activity of the soul. Brehier wrote that the unity of order in Plotinus is higher and anterior to the order itself and that from which the order proceeds.4 âIntelligence or the intelligible worldâ, Brehier went on to remark, âis none other than the very knowledge of the sensible worldâ, that is, informed matter, and âfor the realization of order in matter and for the creation of a sensible world, an intermediary being is required which is active and mobile, extending between Intelligence and matter in so far as the latter is capable of receiving it. This third hypostasis is Soulâ.5 The soul is an order of experience in which things appear meaningiul in as much as in the soul things are conceived through the order of intelligence as the ways the elements in experience are informed. This is the experience characteristic of the mind. The elements in this experience can also be without order, or any relation, in pure sensory experience, where things appear as just brute facts, where even external relations of space, time and proportion are absent. Matter is thus the purely passive recipient of form.
On Armourâs reading, this is the matter of Descartes, which has a determinate nature only as informed by the idea of extension, as an idea of external relations, such as found in mathematical physics, which is a certain way of reflecting on pure sensory experience. A case for this interpretation of Descartes is suggested by Armour, who cites Eustachius a Sancto Paulo as a precedent.6 Descartes insisted that matter âcan be moved in various ways, not by itself but by whatever else comes in contact with itâ (AT 7/26). Thus, a bodyâs motion is conceived through the form of the external relation it bears to another body.
According to Spinoza, emphasis should be on the order of matter as an emanation from the one. Substance as conceived through extension explains its own movement in as much as it is in and conceived through itself. This idea appears in Spinozaâs response to one of Tschimhausâs objections, raised in one of his letters to Spinoza (Ep80). The objection is that it is difficult to understand how, if extended substance is identified with âextensionâ (matter in the Cartesian sense), it can of itself give rise to its own modifications: âI find it very [difficult] ⌠to understand how the existence of bodies having motion and figure can be demonstrated a priori, since there is nothing of this kind to be found in Extensionâ (Ep80). The objection seems to work against Descartes, who understood by matter the chaos of pure sensory experience and the recipient of the form of its movement, but not against Spinoza. Spinoza and Descartes agreed in allowing that from extension alone, regarded in its inertness, no modification can be derived. âFor this reasonâ, wrote Spinoza, âDescartesâ principles of natural things are of no service, not to say quite wrongâ (Ep81). One can no more understand the motion of bodies than the influence of the mind in the activity of a body, according to Descartes. Spinoza was able to explain the activity of bodies on grounds that their activity is essentially the same as that of a thinking substance.
This is, on Hampshireâs reading, the conatus of bodies. On Hampshireâs reading, Spinoza is a kind of materialist, but âhis was a materialism with a difference, if only because the word âmatterâ normally suggests something solid and inert, and no such notion of matter is to found in his writingâ.7 The idea of the conatus of extension, as Hampshire remarked, is absent from Descartesâ conception of matter but is âexactly the concept which biologists have often demanded as essential to the understanding of organic and living systemsâ.8 Spinozaâs matter is self-explanatory, as it is substance; in other words, its modes follow from its essence, or attribute (E1D4, E2D2), and the process by which the modes of substance follow from its nature occurs in thinking substance or substance as conceived through any other attribute, as a function of the conatus, or the âstriving by which a thing strives to persevere in its beingâ (E3P7). Substance can be said to generate its modes through the emergence in being of a certain form of self-reflection, and the conatus is, on this interpretation, simply the subjectâs intuition of this activity.
Aristotelian and Gnostic conceptions of matter, i.e., as the independent recipient of form, drop out of the picture with Spinoza, as extension is no longer considered the given matter of sensory experience without form; rather, it becomes one of the ways Spinozaâs substance gives form to itself. Extension and thought thus stand for two of the ways the one absolutely infinite substance reflects on itself. On the perspectival theory, substance informs itself through extension as the order of classes and measurable properties and through thought as the more concrete order in which the elements in experience are given purpose and fuller meaning. On the intuitionist theory, the former is contained in the latter order, and the difference in attribute is a difference in the immediate intuition of the complete order of self-reflection.
Spinozaâs substance determines itself through infinite attributes (E1D6), and his God âis the immanent, not the transitive, cause of all thingsâ (E1P18). Thus, substance generates its modes within itself, rather than generating these modes by informing an independent being. On the assumption that the cause works on matter as an independent being, it is arguable that a further explanation of the cause must be sought in another application of a form to an independent matter, and this type of explanation, as Spinoza remarked, inevitably gives rise to an interminable and uninformative series of transitive causes (ElApp).
Substance as understood by Descartes differs numerically according to its attribute, and this is why there appear to be as many substances in the writings of Descartes as there are things to be talked about. Thus, extension is one substance and thought is another, and by analogy to Godâs ontological independence each can be said to have a certain independent being. Although Descartes recognized that strictly speaking only God is wholly ontologically independent, Descartes was unwilling to conclude that God is the one substance. With the ontological independence of substance as conceived through any attribute, it follows that if two substances are conceived through different attributes, then they are unrelated. But Descartes apparently ...