A case from 1597 reported at 5 Coke Reports 99b,

and notwithstanding the words of the commission give authority to the commissioners to do according to their discretions, yet their proceedings ought to be limited and bound with the rule of reason and law. For discretion is a science or understanding to discern between falsity and truth, between wrong and right, between shadows and substance, between equity and colourable glosses and pretences, and not to do according to their wills and private affections; for as one saith, ‘talis discretio discretionem confundit.’