From what we have seen thus far, there is little basis for contrasting the utilitarianism of 17th century European philosophy with the spirituality of 17th century Islamic philosophy. Both Spinoza’s and Sadra’s doctrines of knowledge and immortality are deeply philosophical and nondogmatic. They would have understood, I daresay, each others’ theories. But there is already a perceptible division between them, and it is a Cartesian division, though in the opposite way than this is usually conceived. For Sadra asserts that the imaginal power of the mind survives the death of the body. Death is a natural occurrence, but it does not supervene on the failure or exhaustion of the body as, he points out, the physicians and natural scientists maintain; the withdrawal of the soul is not its exhaustion, but an “increasing intensity of its being.”[^26] Descartes maintained the contrary view. Death, he thought, supervenes on the decline and failure of the bodily machine.[^27]

We are mostly taught that Descartes tried to prove that the mind can think, will, perceive and feel without a body, but many of his contemporaries did not understand Descartes to be saying this but something very different. Henry Regius, Descartes’s “wayward disciple,” took his master’s doctrine in a direction perhaps closer to Descartes’s original convictions than the doctrines expressed in the Meditations and defended thereafter. In brief, Regius read Descartes as trying to say that the body could experience, feel, and act, in virtue of the operations of its mechanisms without the need for a soul.[^28]

Spinoza is rarely interpreted as a frank Cartesian materialist, but he knew Regius’s work, and this is the most natural way to take what he says. In the Short Treatise, written about 1662, he expresses himself more clearly on this subject than in the later Ethics. The “mind,” he says in the earlier work, is an idea generated by the body, and the relationship of “union with” is simply the reciprocal of the generation-relation.[^29]

“The Soul is an Idea which is in the thinking thing, arising from the existence of a thing which is in Nature.”[^30] It “has its origin from the body,” and its changes depend “(only) on the body.”[^31] Sensation results from changes in “proportions” between motion and rest in the sensory organs. For instance, more motion in a certain respect can produce sensations of heat, less motion produces sensations of cold.[^32] Mentality arises from the interaction between our bodies and the external world, and the idea of the “mind” arises from our second-order experience of ourselves as first-order sensory experiences. “Because we have now explained what feeling is,” Spinoza says, “we can easily see how from this there arises a reflexive Idea, or knowledge of oneself, experience, and reasoning.”[^33] In the Ethics, he states that mind and body are “one and the same Individual”[^34] and that the mind cannot perceive, imagine, or remember anything without the body:

The human Mind does not perceive any external body as actually existing, except through the ideas of the affections of its own Body”[^35]

The Mind can neither imagine anything, nor recollect past things, except while the Body endures.[^36]

Indeed, Spinoza articulates an inverted image of Sadra’s doctrine that the mind can create the ambient world distinctly belonging to it in arguing that

each physical organism generates the mentality fitting to its distinctive physical organization.

From these two very different ways of conceiving experience and embodiment, much else follows. The Lockean emphasis on “solidity” to which Nasr rightly calls our attention was not unconnected with Locke’s notion that God has given matter the power to think without the need for souls. To be sure this suggestion was disturbing to European philosophers in its own time. Descartes did not want to be associated with it, and Leibniz and Berkeley devoted their brilliance to refuting materialism. Kant did the same. But metaphysics, once having taken on this essentially defensive role in philosophy, was thereafter-and continues to be-haunted by the problem of its own relationship to the world described by science.

Spinoza’s philosophy was not, in his mind, a strange hybrid, but an attempt to synthesize some elements of a long-established metaphysics and ethics with Cartesian elements. Later observers, knowing what came after, seem to be puzzled by the transcendental and unworldly aspects of Spinoza’s philosophy; they see his synthetic project as futile. But in 1670, no one could have foreseen just how deep the rift between the two sets of aspirations, one to improve the human condition through applied science and technology, the analysis and reconstitution of the material, the other to improve it by transcendence of the material could become. For if truth is one, why should not old truths be consistent in the long run with new truths?

Can history reverse itself? That is to say, can there be any unification in philosophy of those aspirations as Spinoza thought there could be? Or any metaphysics dedicated to one quite independently of the other that can exist in harmony with the sciences of the material as Sadra thought? If the scholarly losses I referred to at the start are just one of the visible consequences of this rift that opened up when Spinoza failed to complete his project, it is perhaps reasonable to hope that repairing those losses might help us with the the larger problem from which they stem.