   John Buridan was the medieval author who produced the fullest and most coherent account of singular terms. In his commentary on Aristotle’s De anima, Buridan claims that the vague individual is the most proper singular term. While it is true that the phrase ‘this man’ can lack reference through improper use, if it is used properly it must point to one united existent present object, the very situation in which we form genuinely singular concepts. Demonstrative phrases are so clearly tied to the here-and-now that no problem of identity through time can arise. On the other hand, this allows for only a very time-bound usage. In his consideration of whether the singular term ‘Socrates’ could be defined by the phrase ‘this man’, Buridan remarked that if Socrates leaves the room, he is still Socrates, but he is no longer the referent of ‘this man’. 