Sufism has no secrets into which I have not penetrated; the devout adorer of Deity has revealed to me the aim of his austerities; the atheist has not been able to conceal from me the real reason of his unbelief. The thirst for knowledge was innate in me from an early age; it was like a second nature implanted by God, without any will on my part. No sooner had I emerged from boyhood than I had already broken the fetters of tradition and freed myself from hereditary beliefs.
Having noticed how easily the children of Christians become Christians, and the children of Moslems embrace Islam, and remembering also the traditional saying ascribed to the Prophet, "Every child has in him the germ of Islam, then his parents make him Jew, Christian, or Zoroastrian," I was moved by a keen desire to learn what was this innate disposition in the child, the nature of the accidental beliefs imposed on him by the authority of his parents and his masters, and finally the unreasoned convictions which he derives from their instructions.
Struck with the contradictions which I encountered in endeavoring to disentangle the truth and falsehood of these opinions, I was led to make the following reflection: "The search after truth being the aim which I propose to myself, I ought in the first place to ascertain what are the bases of certitude." In the next place I recognized that certitude is the clear and complete knowledge of things, such knowledge as leaves no room for doubt nor possibility of error and conjecture, so that there remains no room in the mind for error to find an entrance. In such a case it is necessary that the mind, fortified against all possibility of going astray, should embrace such a strong conviction that, if, for example, any one possessing the power of changing a stone into gold, or a stick into a serpent, should seek to shake the bases of this certitude, it would remain firm and immovable. Suppose, for instance, a man should come and say to me, who am firmly convinced that ten is more than three, "No; on the contrary, three is more than ten, and, to prove it, I change this rod into a serpent," and supposing that he actually did so, I should remain none the less convinced of the falsity of his assertion, and although his miracle might arouse my astonishment, it would not instil any doubt into my belief.
I then understood that all forms of knowledge which do not unite these conditions (imperviousness to doubt, etc.) do not deserve any confidence, because they are not beyond the reach of doubt, and what is not impregnable to doubt can not constitute certitude.
The Subterfuges of the Sophists
I then examined what knowledge I possessed, and discovered that in none of it, with the exception of sense-perceptions and necessary principles, did I enjoy that degree of certitude which I have just described. I then sadly reflected as follows: "We can not hope to find truth except in matters which carry their evidence in themselves—that is to say, in sense-perceptions and necessary principles; we must therefore establish these on a firm basis. Is my absolute confidence in sense-perceptions and on the infallibility of necessary principles analogous to the confidence which I formerly possessed in matters believed on the authority of others? Is it only analogous to the reliance most people place on their organs of vision, or is it rigorously true without admixture of illusion or doubt?"
I then set myself earnestly to examine the notions we derive from the evidence of the senses and from sight in order to see if they could be called in question. The result of a careful examination was that my confidence in them was shaken. Our sight, for instance, perhaps the best practised of all our senses, observes a shadow, and finding it apparently stationary pronounces it devoid of movement. Observation and experience, however, show subsequently that a shadow moves not suddenly, it is true, but gradually and imperceptibly, so that it is never really motionless.
Again, the eye sees a star and believes it as large as a piece of gold, but mathematical calculations prove, on the contrary, that it is larger than the earth. These notions, and all others which the senses declare true, are subsequently contradicted and convicted of falsity in an irrefragable manner by the verdict of reason.
Then I reflected in myself: "Since I can not trust to the evidence of my senses, I must rely only on intellectual notions based on fundamental principles, such as the following axioms: 'Ten is more than three. Affirmation and negation can not coexist together. A thing can not both be created and also existent from eternity, living and annihilated simultaneously, at once necessary and impossible.'" To this the notions I derived from my senses made the following objections: "Who can guarantee you that you can trust to the evidence of reason more than to that of the senses? You believed in our testimony till it was contradicted by the verdict of reason, otherwise you would have continued to believe it to this day. Well, perhaps, there is above reason another judge who, if he appeared, would convict reason of falsehood, just as reason has confuted us. And if such a third arbiter is not yet apparent, it does not follow that he does not exist."
To this argument I remained some time without reply; a reflection drawn from the phenomena of sleep deepened my doubt. "Do you not see," I reflected, "that while asleep you assume your dreams to be indisputably real? Once awake, you recognize them for what they are—baseless chimeras. Who can assure you, then, of the reliability of notions which, when awake, you derive from the senses and from reason? In relation to your present state they may be real; but it is possible also that you may enter upon another state of being which will bear the same relation to your present state as this does to your condition when asleep. In that new sphere you will recognize that the conclusions of reason are only chimeras."