  Another main source is the Persian thinker Ibn Sina (Lat. Avicenna), who discusses the concepts of ‘being’, ‘thing’, and ‘the one’ as the primary conceptions of the intellect in his Metaphysics I.5. He introduces the idea of primary conceptions by drawing a seminal analogy between first principles in the order of judgment and in the order of conception: just as there are first principles in the order of judgment, at which the reduction or analysis of propositional knowledge comes to an end (e.g. the principle of non-contradiction), so there are also first principles in the order of conception, which are primitive in the sense that they cannot be defined by appealing to some more general notion. Getting knowledge of them is not making an unknown thing known, but bringing something to mind that was always already known, by means of logically derivative ‘trigger’-notions. The relation between the two most important primary conceptions ‘being’ and ‘thing’, which denote an existential resp. an essential aspect of things, takes the form of a priority of ‘thing’ or ‘essence’, to which ‘being’ is necessarily concomitant. An important other innovation, directly related to the foregoing, was Ibn Sina’s rejection of the theological interpretation of the subject of metaphysics. Since the existence of the subject of a science must be demonstrated beforehand, and God’s existence is to be demonstrated in the science of metaphysics, God cannot be the subject of this science. Moreover, since metaphysics is the first science, nothing else can be its subject, except for something that cannot be demonstrated, since it is self-evident. Hence, Ibn Sina’s declarations that (1) being is a primary conception and that (2) being is the subject of metaphysics are correlated.