  The third kind of synthesis is synthesis of recognition in a concept. To experience objects for Kant, first I have to relate the materials out of which they are constructed to one another temporally and spatially. They may not require use of concepts. Then I have to apply at least the following kinds of concepts: concepts of number, of quality, and of modality (I am experiencing something real or fictitious). These are three of the four kinds of concepts that Kant had identified as Categories. Note that we have so far not mentioned the fourth, relational concepts.