[1, 2] "That [standard, conventional] philosophical concept of meaning has its place in a primitive idea of the way language functions." In the paragraph Wittgenstein is (slyly?) setting the reader up for a fall. Of course one may imagine the builder & his assistant operating in the way described--but the imaginary picture depends upon assumptions about language that are not part of the simple, primitive system. W. as can be seen with the example of the grocer & the 5 red apples, wants to suggest that we know a great deal about how to use language that cannot be captured by Augustine's sweet little fancy, not by the standard positivist theories of language current when W. was writing.
Christopher Robinson & Joseph Duemer read Wittgenstein's Philosophical Investigations