Does Buddhism view mind phenomena as chemical or as supernatural?

I was once again challenged by my scientific friends: who say that all mind phenomena is just chemical reaction! My question is, how does Buddhist philosophy view this question? I'm leaning towards my science friends' view, after reading _A Manual of the Excellent Man_, where the seven aspects of perception on materiality are considered to be the combination of natural elements. If so how does a chemical overpower another, and is the transcendental self also chemical / elements? Because if it were not, then we could assume spiritual forces were active in creation, etc.!