Because they are all born of it, at least in the sense of being 'the flesh of its flesh'. The most recent example is Psychology. What we call psychology existed, in a rude state before there was a science for it. And where was that precursor material studied -- in philosophy.

Wundt and James were philosophers until they showed there was enough understanding to begin directly studying behavior and cognition, without relapsing back into confusion constantly. And then they weren't anymore -- they were psychologists. They literally held academic positions in philosophy and then outside of it.

Likewise for physics, biology, mathematics, etc. Before they had enough structure to cohere, these were studied as philosophy.

Because they are all born of it, at least in the sense of being 'the flesh of its flesh'. The most recent example is Psychology. What we call psychology existed, in a rude state before there was a science for it. And where was that precursor material studied -- in philosophy.

Wundt and James were philosophers until they showed there was enough understanding to begin directly studying behavior and cognition, without relapsing back into confusion constantly. And then they weren't anymore -- they were psychologists. They literally held academic positions in philosophy and then outside of it.

Each science we know of either peeled itself off of a science that was already functioning or emerged out of philosophical considerations. Aristotle may have been a terrible physicist, but he named the discipline and set its boundaries. Alchemy arose out of philosophy, and eventually gave birth to chemistry as a science.

Likewise for biology, mathematics, and even such latecomers as sociology. Before they had enough structure to cohere as independent fields of study, these were studied as philosophy or they were formed as a part of something that originally was.