The basis of homoeopathy is a basic natural principle. In Latin this principle is stated as similia similibus curentur ("Let likes be treated by likes") first propounded by Hippocrates. That is to say, that to cure any disease a drug must be found which is capable of producing similar symptoms when tested on healthy humans. Or in other words, a drug can only cure that which it can produce. The common person understands it as ’poison kills poison’. This principle is described in the Hindu texts as "Vishasya Vishmaushadham".
Everyone knows that iron cuts iron and heat symptoms can be cured by heat treatment. According to science we cannot create anything; we can simply change the form. The things which exist today are because something was already there. A drug, in its proving, can evoke in each case only what was already there, latent in the prover - even as disease brings out only weak points and therefore does not affect two patients in exactly the same way. It requires many provers, of different types and different defective resistances, to bring out the complete picture of a drug pathogenesis.