  Others have taken quantum mechanics to indicate that consciousness is an absolutely fundamental property of physical reality, one that needs to be brought in at the very most basic level (Stapp 1993). They have appealed especially to the role of the observer in the collapse of the wave function, i.e., the collapse of quantum reality from a superposition of possible states to a single definite state when a measurement is made. Such models may or may not embrace a form of quasi-idealism, in which the very existence of physical reality depends upon its being consciously observed.