Language gives sense of thoughts as ordinary things. "Why do we 'thing-ify' our thoughts? One reason is that this enables us to reapply the wonderful machines our brains contain for understanding worldly things." E.g., the method of loci mnemonic technique uses the brain's ability to recognize and represent familiar locations to remember ideas placed at these (mental) locations. "I suspect that, as they're represented in the mind, there's little difference between a physical object and an idea." Indeed, the (at least) temporary permanence of ideas is required for thought to proceed. "No mind can work without some stable states or memories."
NB: This parallels the kinds of observations that Lakoff and Johnson make about pervasive metaphors. Also, the notion of different kinds of permanence of ideas -- related back to previous distinctions of STM and LTM -- are reminiscent of Newell's (1990) discussion of the temporal nature of mental properties. (i.e., the more permanent something is, the more it looks like architecture!!)