  Although this is reminiscent of Descartes in some respects, there is, of course, one crucial difference. For Descartes the fact that one can conceive Thought distinctly from Extension is evidence for the existence of two substances—mind and body. 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. For Spinoza there is only one substance with infinite attributes, and although each attribute is conceived independently from the other/s they still are, nonetheless, all attributes of one and the same substance. It is possible then to conceive, think, or completely explain the entire universe, or everything that exists, under each one of the attributes. That is, we can give a complete physical description of everything that exists, or alternatively explain, describe, or conceive everything as ideas or thought. Being able to explain the entire universe under the attribute of Extension is what allows Spinoza to preserve Descartes’ effort of providing room for progress in the New Science (Cf. Appendix to Part One).