In the classical tradition, one of the divisions of the arts is according to whether they are "liberal" or "servile." 

A liberal art is one that contains within itself its own purpose. It is not ordered toward anything else; it is just good for its own sake.

A servile art is one whose purpose is doing or making something. Its goodness is found in the things it makes. 

Consequently, it is fitting to call theology and philosophy arts, just as much as it is to call sketching and sewing arts: the former are liberal arts, and the latter are servile arts.