  He himself wrote a brief treatise on logic (Tseror ha-Kesef), in which he summarized what he believed were important principles for a correct interpretation of Scripture. His own exegesis applies a variety of techniques: categorizing genera and species, distinguishing between essential and non-essential qualities, asserting the symmetry of relation, understanding the law of contradiction, recognizing valid and invalid syllogisms, as well as logical fallacies. For example, he criticizes commentators who conclude from the truth of a proposition that its individual parts are also true. To illustrate, he cites the verse “There was no man to till the soil” (Genesis 2:5): this verse does not imply that there were at the time no human beings—a proposition at variance with the Aristotelian thesis (to which Kaspi apparently subscribed) that the world has always existed alongside God.