When we compare what Spinoza says about the relations between the idea and the idea of the idea in the Tractatus de Intellectus Emendatione with what he says about them in Part II of the Ethics, we get the impression, at first glance, that there are a number of contradictions between these two texts. Indeed,

1. In Paragraph 33 of the Tractatus de Intellectus Emendatione, Spinoza claims that an idea can be the object of another idea. With Propositions 20 and 22 of Part II, by contrast, he demonstrates that there is necessarily an idea of every idea. This, however, is not exactly an insurmountable contradiction. For, after all, what is necessary is a fortiori possible. And in order to prove, inversely, that the existence of an idea of the idea corresponding to each idea is not simply possible, but also necessary, we must presuppose the whole of Spinoza's ontology: the definition and the existence of God, the unicity of substance, the parallelism of attributes, etc. But none of this would have been available to readers of the TdIE: the goal of that work is, on the contrary, to lead readers, from wherever they might be, to the progressive discovery of the premises of Spinozist ontology, which consequently cannot be posited at the outset. Generally speaking, the mere absence of a claim found in the Ethics from the TdIE proves nothing.

2. There is, however, a more serious contradiction. In Paragraphs 33 and 34 of the TdIE, Spinoza insists that the idea of the idea is something other than the idea of which it is the idea. In the Scholium to Proposition 21 of Part II of the Ethics, by contrast, he demonstrates that the idea and the idea of the idea are in reality one and the same thing. And yet, this is perhaps not a formal contradiction either. For two things can be one under a certain relation, all the while remaining distinct under a different relation. And that this is the case here is confirmed by the very demonstration that Spinoza gives of the identity between the idea and the idea of the idea.