The last rule was to make enumerations so complete, and reviews so comprehensive, that I should be certain of omitting nothing. - René Descartes

For ’tis not enough to have good faculties, but the principal is, to apply them well.

Los orígenes del método están, según nos cuenta Descartes ( Discurso), en la lógica, el análisis geométrico y el álgebra. Conviene ante todo insistir en que el gravísimo defecto de la lógica de Aristóteles es, para Descartes, su incapacidad de invención.

I suppose therefore that all things I see are illusions; I believe that nothing has ever existed of everything my lying memory tells me. I think I have no senses. I believe that body, shape, extension, motion, location are functions. What is there then that can be taken as true? Perhaps only this one thing, that nothing at all is certain ... But I cannot forget that, at other times I have been deceived in sleep by similar illusions; and, attentively considering those cases, I perceive so clearly that there exist no certain marks by which the state of waking can ever be distinguished from sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I am now dreaming ... I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake ... There is nothing more ancient than the truth.