IBN SÎNÂ’S (LATIN ‘AVICENNA’) treatise al-Burhân (On Demonstration) of his Shifâ’ closely follows Aristotle’s Posterior Analytics, but on at least two points it significantly diverges.1 The context for these differences is the issue of the proper methodology for scientific inquiry and the question “How does one acquire the first principles of a science?” That is to say, how does the scientist arrive at the initial axioms or hypotheses of a deductive science without inferring them from some more basic premises? The ideal situation, Ibn Sînâ tells us, is when one grasps that a per se relation holds between the terms, which would allow for absolute, universal certainty. Ibn Sînâ then adds two further, perhaps more interesting, methods used by ancient and medieval scientists for arriving at first principles. These are Aristotelian induction (Arabic istiqrâ’, Greek epagôgê) and examination or experimentation (Arabic tajriba, Greek empeiria). Ibn Sînâ severely censures Aristotelian induction as he understood it; for he argues that it does not lead to the absolute, universal, and certain premises that it purports to provide. In its place, though, he develops a method of experimentation as a means for scientific inquiry, and although experimentation cannot provide “absolute” principles, the natural sci entist can use experimentation to discover “conditional,” universal principles, which can function as first principles in a science.