One of the most powerful thoughts people have is the thought of necessity. It is much more than a thought. The word 'necessary' means 'it cannot be otherwise', and the Latin root means 'don't yield'.
. . .
This notion of necessity is crucial to our whole ordering of thought; as is its opposite, which is contingency. 'Contingency' means 'what can be otherwise'. If something can be otherwise, its [sic] meaningful to try to change it. If it cannot be otherwise, then there's no use trying. This will have a tremendous effect.
~David Bohm, Thought as a System, Routledge, London 1992, pp. 68-69.
This image I stumbled upon some months ago at a myspace page -- no credit listed.