Reality is the state of things as they actually exist, rather
than as they may appear or might be imagined. In a wider
definition, reality includes everything that is and has been,
whether or not it is observable or comprehensible. A still more
broad definition includes everything that has existed, exists,
or will exist. Philosophers, mathematicians, and other ancient
and modern thinkers, such as Aristotle, Plato, Frege,
Wittgenstein, and Russell, have made a distinction between
thought corresponding to reality, coherent abstractions
(thoughts of things that are imaginable but not real), and that
which cannot even be rationally thought. By contrast existence
is often restricted solely to that which has physical existence
or has a direct basis in it in the way that thoughts do in the
brain. Reality is often contrasted with what is imaginary,
delusional, (only) in the mind, dreams, what is false, what is
fictional, or what is abstract. At the same time, what is
abstract plays a role both in everyday life and in