The test of friendship is assistance in adversity, and that too, unconditional assistance, Co-operation which needs consideration is as a commercial contract and not friendship. Conditional co-operation is like adulterated cement which does not bind.
Colouring does not depend on where the colours are put, but on where the lights and darks are put, and all depends on form and outline, on where that is put.
Common sense invents and constructs no less than its own field than science does in its domain. It is, however, in the nature of common sense not to be aware of this situation.