A Short History of Modern Philosophy: From Descartes to Wittgenstein, Second Edition by Unknown Author Page A

single divine substance, since it can be conceived in itself and there is nothing beyond itself by reference to which we must conceive or explain it. It has modifications— specific thoughts, images and agglomerations of the same—just as extension has its modifications. But in the rational explanation of these it is to thought alone that we need refer; having referred to thought, we do not need to go beyond it to some more basic attribute through which thought itself must be conceived. This explains why the properties of thought are pellucid to us (although it is clear on reflection that thought and extension are pellucid in a different way and for different reasons). Thought, therefore, is another attribute of the divine substance.
    While there are of necessity infinitely many such attributes, to finite beings only finite knowledge is available. Thus we can conceive God through the attribute of extension and through that of thought, while other manners of conception lie outside our intellectual capacity. In so far as the world is knowable to us, therefore, it consists of one thing, seen under two aspects, which correspond to its two knowable attributes. It can be seen either under the aspect of thought, in which case we call it God, or under that of extension, in which case we call it Nature. God or Nature (Deus sive Natura) is the single existing thing which exists of necessity and, being cause of itself, persists through all eternity. Thought and extension are not mere properties of God: they each constitute God’s essence, and each therefore present to the intellect a full and adequate idea of what God is.
    It is of course extremely puzzling to imagine in this way one thing with more than one essence: the concept of an ‘attribute’ only seems intelligible when construed epistemologically, as a reference to the two possible ways of knowing God; the alternative, ontological, conception, which attributes two separate essences to God, is extremely difficult to understand. But Spinoza definitely meant us to construe his theory ontologically, believing that only then will the full intellectual consequences contained in the concept of substance be understood. Only then could it be seen that the very same ontological argument that shows the existence of a substance, explains also the existence of thought and of extended matter. There ceases to be a distinction between creation and the creator, and the greatest theological problem therefore dissolves. Likewise there ceases to be a real distinction between mind and matter: so the greatest metaphysical problem also dissolves. Mind, matter, creation, creator—all these are simply names of the same eternal self-sustaining thing.
    Mind and its place in nature
    The theory of the attributes was partly intended by Spinoza to solve an outstanding question raised by Descartes’ philosophy of mind. If the mind is, or belongs to, a separate substance from that of the body, then how do mind and body interact? What mechanism can join two substances, so that changes in the one are explained by changes in the other? On Spinoza’s reading of ‘substance’ the suggestion is a nonsense, and his reading, he thought, is the only consistent one.
    Spinoza’s solution to the problem of mind and body is ingenious, although hard to understand in its entirety. The mind and the body are one and the same thing, which is conceived now under the attribute of thought, now under the attribute of extension.’ The theory of the attributes implies not only that the one substance can be known in two ways, but that the same two ways of knowing apply also to the modes of that substance. The mind is a finite mode of the infinite substance conceived as thought; the body is a finite mode of the infinite substance conceived as extension—and these two finite modes are in fact one and the same. Spinoza summarises the theory by saying that the mind is the idea of the body.
    However, when we describe a mode of