Literature & philosophy
He who knows only his own side of the case, knows little of that.
John Stuart Mill, On Liberty, chapter II. Mill argues that understanding opposing reasoning is part of understanding your own position.
An example
Suppose you favor longer opening hours. A serious objection might concern staffing cost rather than resistance to growth. Addressing that cost is more useful than dismissing the objection as negativity.
Try it
State your position, the strongest objection to it, and the evidence that would change your mind.
More context
John Stuart Mill, On Liberty, chapter II. Mill argues that understanding opposing reasoning is part of understanding your own position.
Sources & further reading
John Stuart Mill · On Liberty