(quote from RealReality.org/Real_Faith_and_Reason_Vol_2_-_Scientia.pdf)

The Depth of Misunderstanding

Consider the following quote from Critical Thinking, Second Edition:

“Assumption: An assumption is something we take for granted or presuppose. Usually it is something we previously learned and do not question. It is part of our system of beliefs. We assume our beliefs to be true and use them to interpret the world about us. . . . If our belief is a sound one, our assumption is sound. If our belief is not sound, our assumption is not sound. Beliefs, and hence assumptions, can be unjustified or justified, depending upon whether we do or do not have good reasons for them.”

This statement from “Critical Thinking, Second Edition” says that an assumption is something we “take for granted or presuppose.” That is, we accept the assumption without proof. Then it says that assumptions can be “justified or unjustified” depending on whether we have “good reasons for them.” But what would be a good reason for believing something that we have no sane reason to believe?

Indeed, the only way we can use an assumption as part of sound reasoning is if we prove that the assumption is true, but if we prove that the assumption is true, it’s not an assumption. Rather, it’s a proved fact. And yet we believe an assumption without a reason to believe it. So the critical thinking book is telling us there’s sometimes a good reason to believe some claim when there’s no good reason to believe the claim.

We can see the depth of the problem. Since so many authoritative sources use irrational thinking, we think it’s sane to think irrationally. We become calloused, and we don’t even notice the insanity. Schools teach irrational thinking as “sound reasoning” and “critical thinking,” so students lose the ability to tell the difference between sanity and insanity. Since ungodly thinking can’t possibly have true premises, secular schools accept irrational thinking patterns as not only normal but the only option.

(end quote)