Since then the term 'utopia' has often been used for similar descriptions of ideal states, of which there have been quite a few, and as the adjective 'utopian' to qualify political plans, usually in the sense that even if the plan sounds well and would desirable if widely practised, in fact it is impracticable, usually because human beings are on average not much like the utopian planner conceived them to be.

And indeed, one main constraint on all political plans and proposals, especially including the more utopian and idealist ones, is that in terms of their very own moral norms most human beings have been immoral most of the time, and practised what they preached only if doing so came with little risk and little costs to themselves. (See: Ovid).