Solipsism, in philosophy, is an extreme form of subjective idealism that denies that the human mind has any valid ground for believing in the existence of anything but itself. It is the theory that ‘the self’ is all that exists or that can be proven to exist.
“I am my world.” – Ludwig Wittgenstein
Presented as a solution of the problem of explaining human knowledge of the external world, it is generally regarded as a reductio ad absurdum (the method of proving a statement by assuming the statement is false and, with that assumption, arriving at a blatant contradiction).
More colloquially, solipsism is defined as self-absorption, an unawareness of the views or needs of others: the quality of being self-centred or selfish.
“But what can a decent man speak of with most pleasure? Answer: Of himself. Well, so I will talk about myself.” – Fyodor Dostoyevsky, Notes from Underground