The reply to you is:

The intellect establishes only universal concepts considered without qualification. It does not establish anything particular except through something else, such as sensory perception and its adjuncts. This is why a rational, logical syllogism yields no conclusion unless it contains a universal proposition. If we wish to bring particular things under universal propositions, we must conceive of those particulars separately from our conception of the universal propositions.

Thus, suppose we know that everything either subsists in itself or in something else; that every existent is either necessary in itself or contingent in itself; that every existent is either beginningless or brought into existence; and that every existent, or every contingent thing, is either a substance or an accident. If we then wish to judge that a particular thing is beginningless or brought into existence, a substance or an accident, necessary or contingent, or the like, we must identify it through something other than that by which we knew the universal proposition. Conceiving of the particular thing included under a universal proposition is one thing; conceiving of the universal proposition is another.

Let the discerning reader reflect on this, so that it becomes clear to him that whoever does not establish an existent that can be perceived by the senses establishes only universal propositions in the mind. This is like their establishing number in the abstract, magnitude in the abstract, realities in the abstract, and existence in the abstract. All these are things established in the mind, not things existing in concrete reality.

Therefore, whoever affirms that there is a necessary, beginningless existent, yet says that it is impossible to point to it, cannot regard it as a determinate entity with its own distinguishing characteristics. It must instead be an unrestricted abstraction in the mind, with no reality outside it.