Evil demon

The evil demon, also known as evil genius, and occasionally as malicious demon or genius malignus, is a concept in Cartesian philosophy. In his 1641 Meditations on First Philosophy, René Descartes hypothesized the existence of an evil demon, a personification who is "as clever and deceitful as he is powerful, who has directed his entire effort to misleading me." The evil demon presents a complete illusion of an external world, including other minds, to Descartes' senses, where there is no such external world in existence. The evil demon also presents to Descartes' senses a complete illusion of his own body, including all bodily sensations. Some Cartesian scholars opine that the demon is also omnipotent, and thus capable of altering mathematics and the fundamentals of logic, though omnipotence of the evil demon would be contrary to Descartes' hypothesis, as he rebuked accusations of the evil demon having omnipotence.

It is one of several methods of systematic doubt that Descartes employs in the Meditations.

Another such method of systematic doubt is the deus deceptor (French dieu trompeur), the "deceptive god". Cartesian scholars differ in their opinions as to whether the deus deceptor and the evil demon are one and the same. Among the accusations of blasphemy made against Descartes by Protestants was that he was positing an omnipotent malevolent God.

Kennington states that the evil demon is never declared by Descartes to be omnipotent, merely to be not less powerful than he is necessarily deceitful, and thus not explicitly an equivalent to an omnipotent God. The evil demon is capable of simulating an external world and bodily sensations, but incapable of rendering dubious things that are independent of trust in the senses, such as pure mathematics, eternal truths, and the principle of contradiction.

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