Certain cognitive and philosophical aspects of the concept of conceivability with intended or established diversion from reality are discussed. The “coherence gap problem” arises when certain fragments of the real world are replaced with imaginary situations while most details are ignored. Another issue, “the spectator problem”, concerns the participation of the conceiver himself in the world conceived. Three different examples of conceivability are used to illustrate our points, namely thought experiments in physics, a hypothetical world devoid of consciousness , and (...) virtual reality. (shrink)