First of all science is a branch of philosophy albeit one that puts the rest of the tree in the shade. I would argue that the reason for this is because it has a means for testing its ideas and is therefore useful.
Susan Haack says this
all the stuff there is is physical but what’s going on between our minds and the world around us is not all physics.
I would argue that yes it is, but it is too complex to analyse in physics terms. This is actually not uncommon. At its basic level all human history is just fundamental particles whizzing around interacting with each other. However, if we want to understand why Henry VIII divorced Catherine of Aragon, we don't call Brian Cox.