But persons and their bodies have different identity conditions and are both substances, so there are two substances essentially involved in a human being, hence this is a form of substances dualism.
For Spinoza, this is not the case, and this is the point he is making in this central proposition (1P10), namely, that although two attributes may be conceived independently one without the other this does not imply that there are two substances existing separately.
There were five substances that should not have been in his system, but they said that it was only tiny amounts.
McTaggart argues that we perceive that there are many substances, but also holds that it is a priori that, if there is one substance, then there are many, since it is a priori that every substance has infinitely many parts.
There is one substance with which nickel does react - in 1889, the German-born chemist Ludwig Mond noticed that nickel pipes corroded in the presence of carbon monoxide.
Material distinction is a necessary and sufficient criterion for real difference, traditionally conceived, whereas there is formal distinction if and only if there is one substance in number (i.e. material identity in the strict sense) and a multiplicity of formal principles with different descriptions instantiated by it.
According to Descartes there are two kinds of substances, a material, extended substance and an immaterial, thinking substance.
From this he proves that there cannot be two substances with the same attribute, since each would limit the other.
There could not be two substances in the universe, Spinoza argued, one physical and the other divine, since this involved a logical contradiction.
He does not begin from a single highest kind, but rather lists the following as the ten highest categories of things "said without any combination" (Categories 1b25): There are two sorts of substance: a primary substance is, e.g., an individual man or horse; the species (and genera) of these individuals (e.g., man, animal) are secondary substances.
When Irigaray says that human nature is two, she does not mean that there are two fixed sexual substances, but that to be natural is to be embodied, finite, divided, that the fundamental character of nature is growth through differentiation.
