Internal and external are arbitrary divisions anyway and studying Philosophy led me to consider how we can ever truly know whether our perceptions agree with external "things in themselves" anyway. The Alice In Wonderland world of quantum physics shows us that nothing is quite what it seems, and solidity is an illusion. Atoms mainly consist of nothing, the space between electrons (which are said only to exist in a probability cloud) and the nucleus, made up of protons and neutrons. To explain what constitutes these elements, scientists are currently clutching at quarks (which possess among other properties, strangeness and charm!), because they're not quite ready to admit that nothing is actually there at all. They're creating theories, as thinking creates things. Everything is energy, even e-motion is energy in motion, and energy itself is an illusion, a tension created by thinking what we see is not ourselves. There is just nothing perceiving its own nothingness and everything is that perception. The answers are everywhere and in everything (and in nothing, as everything and nothing are the same: now here = nowhere, zero is an infinite circle). You are the answer to yourself, and it's all about perception. That's why I = eye, and e=mc2 is 2cme (to see me) backwards; the world is a reflection of your mind, and you have the answers within you. This is why self-awareness and self-fulfilment are so important too.