Not everything has a physical opposite, even if we can fabricate one for sake of discussion.
Example: There is "orange", the actual fruit, what one might call orange-rupa, and there is "orange", the concept, the idea, the name, the definition, orange-nama, the pointer I've just used several times now to reference orange-rupa. The two are derived from eachother: orange-rupa is the origin of orange-nama, but orange-nama is the way in which we understand orange-rupa. However, "not-orange" is itself just a concept, a negation of orange, and it has no physical correlate. Orange did not arise from "not-orange". You could use "not-orange" to specify everything orange might've arisen from, in dependence on it, and that would be correct, but then, you're not actually describing anything at all, just playing games with language in a way that's confusing. Hence, the world probably didn't begin with Yin and Yang, Yab-Yum, 3 Gunas, or whatever other grandiose and superstitious simplification.
So, in conclusion, I don't really need to know everything that's "not-orange" to eat an orange. Studying apples -- which are not orange -- tell me much less about oranges than oranges themselves. And in order to experience an orange, I don't even necessarily need a concept for orange at all. Without any preconceptions at all, with mindfulness I can eat an orange and know what it tastes like.
Similarly, without any preconceptions and with mindfulness, you can find happiness and develop compassion.