sentences:  According to Alexander Rosenberg philosophers mostly these days believe that reduction between sciences is possible "in principle" but concepts we currently have do not allow reductions even in many cases in which natural sciences are involved, for instance from biology to chemistry.Often, the extent to which one theory can be said to be reduced to another theory is complicated by the existence of emergent phenomena.Furthermore, there is the issue of by what criteria one judges one theory as more fundamental than another.