This is the claim: Human knowledge expresses itself in three different modes: explicit, implicit, and sensory (e.g., visual) knowledge. The reference to knowledge as explicit knowledge only (as it is usually done) neglects the other modes of knowledge. Instead of using the noun "knowledge," it is suggested that we use "knowing" as a term to stress the active mode in cognition. The three modes of knowing are reflected in different mechanisms of cognitive and neural processing; these can already be observed in classical documents of humankind. This unity of the different modes of knowing can also be extracted from cultural artifacts such as poetry. Although possessing different characteristics, the three modes of knowing are related to each other in a complementary way, thus providing an integrative network for cognition. We suggest that a unifying frame of the modes of knowing lies in aesthetic principles. These different modes of knowing with their unifying frame reflect some general features of cognition. We stress that basic concepts in "artificial or machine intelligence" do not match at all human modes of knowing.