Letter 56: When you ask if I have a clear vision of God as I do of a triangle, I answer in the affirmative. But if you ask me if I have a spiritual image as clear of God as of a triangle, I answer negatively. We cannot imagine God, but we can grasp him through the intellect. It must also be said here that I do not claim to have a complete knowledge of God, but that I understand some of its characteristics – not all or most – and it is certain that my ignorance of many properties does not prevent me from knowing some of them. When I studied the elements of Euclid, I realized early on that the three angles of a triangle are equal at two right angles, and I clearly recognized this characteristic of a triangle, even though many others did not know it. Although this is reminiscent of Descartes in some respects, there is of course a decisive difference. For Descartes, the fact that thought can be clearly conceived from extension is evidence of the existence of two substances: the mind and the body. For Spinoza, this is not the case, and this is the point he points out in this central sentence (1P10), namely that even if two attributes can be conceived independently – one without the other – it does not mean that there are two substances that exist separately. For Spinoza, there is only one substance with infinite attributes, and although each attribute is designed independently of the others/s, they are all attributes of the same substance. It is then possible to conceive, think or completely explain the whole universe or everything that exists under each of the attributes. This means that we can give a complete physical description of everything that exists, or, alternatively, explain, describe or conceive just like ideas or thoughts.
The ability to explain the entire universe under the “extension” attribute is what allows Spinoza to preserve Descartes` efforts to make room for progress in New Science (see Appendix to Part 1). This: All ways of thinking have God for one thing, to the extent that he is a thinking thing, and not to the extent that he is explained by another attribute (by 2P6). So what makes the mind is meant for thought is a way of thinking and not of enlargement, that is to say (by 2D1), it is not the body. He was the first. Before discussing the theory of attributes in ethics, it will be useful to keep in mind a rudimentary sketch of the general structure of Spinozas Ontologie: Spinoza defines the term “attribute” in definition 4 of the first part of ethics as follows: “Per attribute intelligo id, quod intellectus de substantia percipit, tanquam ejusdemti constitute.” That is, “With an attribute, I understand what the intellect of substance takes for its nature.”  Nevertheless, it is surprising how little agreement there is among scholars on some of the most fundamental features of Spinoza`s attribute theory.