I would add that the cumulative effect of all these examples in SICP is to demonstrate that you can solve any programming problem from first principles - that i

I would add that the cumulative effect of all these examples in SICP is to demonstrate that you can solve any programming problem from first principles - that is, by combining a few simple but powerful constructs in the several ways they describe. Moreover, a solution constructed this way might be simpler and easier to understand than a solution made the more usual way: by looking for a specialized language construct or library that seems to offer an already-made solution to the problem.