  Further building on the insistence that all knowledge comes from the senses, Gassendi discusses the view (shared as well by Descartes and the Aristotelians) that there are propositions we can know with certainty. Since all propositions are judged as true or false on an empirical basis, none can be deemed indubitable, save those of theology and theologically-derived cosmology. This lack of certainty extends as well to logical demonstration, whether of inductive or deductive character. Nothing is certain about such demonstration, Gassendi suggests, save the limits imposed upon it by the frailty of human intellectual capacities. The natural bounds of our epistemic grasp in the physical sciences, astronomy, or most any other field of study is just what the senses tell us, plus any correctives reason supplies on the basis of sensory-based knowledge we have already accrued.