Many are extremely brief, some seem unhelpful or invalid. Beware that this God is not a person and does not choose anything. Nonetheless, Thought is one of his attributes. We will make a feeble attempt at reconstructing the first few propositions. We will see later how this proposition is used, which is a better clue to its meaning.
Ambiguities remain here.
Spinoza's view seems to be that substances would differ in one attribute if and only if they differ in all of them. This one is easy. If they have nothing in common, then by 1a5, the concept of one cannot involve the concept of the other. It follows that if they have nothing in common, then one is not the cause of the other. Suppose the substances did not differ except numerically, i.e. , that the two were exactly alike.