Chap wrote:I can't ever imagine deliberately making two contradictory statements to them, and if I did I can't see what possible good it would do.
Chap, I shouldn't be too hard on you; eight or nine years ago I would have thought the same way; but now I see your attitude as incredibly naïve.
Let's see if I can come up with an example that illustrates my point. Assume for a moment that you have a son or daughter who's fifteen, on the verge of learning how to drive. You take your child for a drive and you come up on two signs by the side of the road, one that says, "Keep right except to pass," and the other right next to it that says, "Do not pass." (I actually once saw both of these signs side by side on one stretch of road, so this isn't an artificial example.)
If we assign "pass" to predicate P, and "keep right" to predicate R, then the two signs are R or P and not P. At this point you simply apply a form of modus ponens and conclude from the two signs R. With the two signs together application of the predicate P is redundant.
Now this isn't a contradiction, but it is still a form of the same problem; the problem is that the pass in "Keep right except to pass" and the pass in "Do not pass" don't mean the same thing! The former pass refers to passing on the right side of the central yellow line and the latter pass refers to crossing the central yellow line to pass.
So my question to you, Chap, is, what do you tell your fifteen-year-old about these two signs side by side? Do you tell her/him, it says, "Keep right except to pass," and, "Do not pass," but it really means blah blah blah, and end it at that, or do you tell your fifteen-year-old precisely the same thing and then add, here's an example of someone using the same term in two different places but meaning different things in the different places? In other words, do you give your child just enough information to process the pair of signs, or do you do a more complete job of preparing your child for many cases in the outside world where a term is used twice but means different things each time they're used?
As young children of course we need logical consistency from our parents. It would make no sense to show the mentioned pair of signs to a four-year-old and expect such a young child to understand what they meant. But it is also our job as parents to, with time, prepare our children for what they're going to encounter in the world, and that includes some of the subtleties of the language. If an eighteen-year-old leaves home for college with the impression that every statement anyone makes needs to be mathematically precise, then that eighteen-year-old's parents have done a poor job of parenting.
