Might what you call "informal logic", or "reasoning" just be "common sense"?
You know, the common snese to not put your hand on a hot stove.
Common sense has some validity, as far as figuring things out.
2 + 2 = 4 makes sense, and could be "common".
the earth is flat makes sense, and is "common".
It makes sense that the earth is flat--after all, you never see it curve, so long as you're on the surface.
Common sense also says things like "don't get wet and cold--you'll get sick".
Some of this is quite valid, some quite erroneous (flat earth). As a general idea, I would say that common sense is valid.
Maybe some others can expound further on this.
All a man's knowledge comes from his experiences
™ Version 4.2