The phrase "sound logic" means having a logical and reasonable way of thinking or decision-making. It refers to using facts, evidence, and reasoning to come to a sensible and rational conclusion or solution.
Sentences with «sound logic»
Common sense, facts and sound logic of the kind displayed in your post are not appreciated on this site. (justarsenal.com)
And they must always use sound logic when developing their arguments. (wattsupwiththat.com)