Sure test to check the absence of desire?

Q: Sweet Mother,

How can we know that our acts, our thoughts and our aspirations are not tainted by vital desire, though they may seem right to our common sense?

It is a question of inner sincerity. Common sense is not a judge because it is a mental function of a rather inferior order.

Moreover, there is a very simple way of knowing. One has only to imagine that the thing one wants to do will not be done, and if this imagination creates the least uneasiness, then one can be sure of the presence of desire.

Ref: Some Answers from The Mother