Plato concludes that there must be something perfect beyond this imperfect world by
reasoning that if the impermanent and imperfect here and now was all there is and if
knowledge derives only from what one perceives through the senses, how would one have
any conception of perfection? It stands to reason, for example, that even though at best we
can only act on Earth in ways that approximate perfect virtue, we yet have a sense of what
perfect virtue is. Where does that ideal come from if our senses are our sole source of
knowledge and what they reveal is only imperfection? Hence, his logical conclusion (note the
process of reasoned deduction at work) that there is a world of Ideal Forms or essences (a
world of pure thought or spirit) of which this world is an imperfect imitation.