Locke, 1690, Preface to the Second Treatise on Civil Government:

If any one, concerned really for truth, undertake the confutation of my Hypothesis, I promise him either to recant my mistake, upon fair conviction; or to answer his difficulties. But he must remember two things.

First, That cavilling here and there, at some expression, or little incident of my discourse, is not an answer to my book.

Secondly, That I shall not take railing for arguments, nor think either of these worth my notice, though I shall always look on myself as bound to give satisfaction to any one, who shall appear to be conscientiously scrupulous in the point, and shall shew any just grounds for his scruples.