We there showed that the idea of body and body, that is, mind and body (II. xiii.), are one and the same individual conceived now under the attribute… - Benedictus de Spinoza

Will and intellect are one and the same thing.

...If we had the time we should now go on to present the ingenious theory of organism with which Spinoza focused the general ontological scheme specifically on the biological sphere, where mentality is ordinarily seen to be conjoined to physical fact, and particularly on the case of man. It must be enough to say that Spinoza makes it beautifully intelligible from his general premises that the quality and power of a mind are proportionate to the complexity of the body to which it corresponds, so that the perfection of the human body as a piece of physical organization is a direct yardstick for the perfection of the human mind which, as it were, conformally (or: isomorphously) duplicates the body's physical performance on the plane of thought.

Descartes... fell back on his original confusion of matter with space—space being, according to him, the only form of substance, and all existing things but affections of space. This error... forms one of the ultimate foundations of the system of Spinoza.

His [Spinoza's] correspondence is the most interesting book one can read in the world of uprightness and of humanity. [Original in German: Sei Briefwechsel sei das interessanteste Buch, das man in der Welt von Aufrichtigkeit, Menschenliebe lesen könne.]