We've already taken a look at a strong objection to Platonism's view of abstract objects. This was based on a causal argument against the idea that abstracta exist independently of the mind. Given their necessity, then, abstracta are demonstrated to be concepts of a divine mind via reductio ad absurdum. However, are there any positive, direct reasons to accept conceptualism?
One possibility would involve the argument from intentionality. It appears as though statements, such as "2+2=4," "all bachelors are unmarried," and "Jones is sitting under a tree in W," are all about something. That is to say, propositions, if they have any meaning, seem to be intended, or to have intentions. Yet, intentions do not exist independently of persons. Without the existence of a mind that intends meaning in a statement, the statement is just a set of words.
Given the intentionality of propositional statements, therefore, along with the necessity of at least some propositions, we have good reasons to believe that the Conceptualist Argument provides a rational basis for theism.