It is a requirement that our brains have a model of the world as it truly is. Otherwise we could not adapt to and survive in it.

Lakoff and Johnson, in 'Philosophy in the Flesh' that I refer to in my post above, have a different take on this. They suggest that our brains do not have a model of the world-as-it-is, in the objective a priori sense, as it 'truly is'; in fact, that it is impossible for our brains to have such a model.

Instead, our concepts and modelling of the world are good enough for us to survive and flourish, without being 'true'; indeed, evolution demanded that this be so. And also, because human bodies and neural activities are so similar amongst humans, we have similar basic models - we all agree whether the 'cat is on the mat' or not.

By introducing the word 'truly' in your comment, you imply a whole lot of metaphysical baggage that is not necessary. And if you omit it, by not insisting that we must perceive a 'true', objective world-as-it-really-is independent of human observers, then you avoid much of the 'hard' problems that Western metaphysics is caught up in, and yet can retain all the realism you want to explain how our actions in the world can be so effective.

I cannot possibly do justice to their argument in a short post. They are not denying that there is an objective world independent of human observers - only that if there is, we can never know it. But what we *do* know - the product of an interaction of whatever is 'out there' and our embodied mind - is good enough for stable knowledge of the world and our ability to act effectively in it.

Of course, you can define 'true' as that perception of the world which is effective (in fact, that is what they do). But your use of it implies the traditional metaphysical as-it-is interpretation.

This may appear inconsequential hair-splitting, but to me it has profound consequences - and again, I can only refer you to the book for a full and readable version of what these consequences are.