Uniquely human temporal thoughts

Life on Earth will eventually come to an end. The thought expressed in the previous sentence is about a point in time that is not known to the individual entertaining the thought. This paper is concerned with the nature of such temporal thoughts. We propose that the capacity to mentally represent thoughts about non-specific temporal intervals is a unique aspect of human cognition. We suggest that this capacity is a consequence of the fact that human grammar defines/generates sentences involving binding of temporal variables and quantification over intervals. This leads to a view of language evolution as transition between logics.