“All the prejudices I here undertake to expose depend on this one: that men commonly suppose that all natural things act, as men do, on account of an end; indeed, they maintain as certain that God himself directs all things to some certain end” (Spinoza, Collected Works vol. I, Curley trans., p. 439).
“[I]t follows, first, that men think themselves free, because they are conscious of their volitions and their appetite, and do not think, even in their dreams, of the causes by which they are disposed to wanting and willing, because they are ignorant of [those causes]. It follows, secondly, that men always act on account of an end, viz. on account of their advantage, which they want. Hence they seek to know only the final causes of what has been done, and when they have heard them, they are satisfied, because they have no reason to doubt further” (p. 440).
“Hence, they consider all natural things as means to their own advantage. And knowing that they had found these means, not provided them for themselves, they had reason to believe that there was someone else who had prepared those means for their use. For after they considered things as means, they could not believe that the things had made themselves; but from the means that they were accustomed to prepare for themselves, they had to infer that there was a ruler, or a number of rulers of nature, endowed with human freedom, who had taken care of all things for them, and had made all things for their use” (pp. 440-441).
The famous appendix to book 1 of Spinoza’s Ethics, from which the above is excerpted, is a sort of psychological exposé of the superstition-like attitude behind the kind of “external” teleology that sees everything in terms of ends, but treats all ends as resulting from the conscious aims or will of a supernatural being or beings, more or less on the model of what theologians have called “particular providence”.
But though he explicitly refers only to this kind of conscious providence that implies ongoing supernatural intervention in the ordinary workings of the world, he nonetheless in an unqualified way dismisses all explanation in terms of ends. At the same time, the notion of determination or causality that he does acknowledge as genuine is too narrow and rigid (too univocal). (See also Thoughts on Teleology.)
Most of the historic criticisms of Spinoza have been extremely unfair; this includes remarks by Leibniz, Kant, Fichte, and Hegel. Spinoza rightly pointed out that we tend to overrate the role of conscious intentions in human affairs and the workings of the world. But Leibniz rightly pointed out that Spinoza’s exclusive emphasis on unconditional divine power or omnipotence (as contrasted with goodness) — which reduces everything to efficient causes — has undesirable consequences.