An Unwritten Law?

When I was teaching at Tanglewood, Earl brought me a composition with which I was generally satisfied. We only stopped at one place. There was some kind of mistake there but we could not figure it out. We corrected that place and everything seemed fine for the moment. But I was still not satisfied and I thought about it until the next day. I kept a visual picture of the score in my mind and suddenly realized that, indeed, that place had been wrong, but the real mistake had occurred some twenty measures earlier, and from that point forward, the entire composition was off course. Since I did not know the score perfectly, I waited until I met Earl at lunch. When I spoke to him, he told me that he, too, had found the mistake and that it was several measures before the place we had tried to correct in our lesson. I was pleased that he had found it on his own, but I was curious if his discovery was the same as mine. I was not completely sure because I did not know the score well enough from memory; I merely had a recollection of what it looked like. Thus we immediately set out for his apartment to look at the score. And lo and behold, the mistake was in the exact same measure. And we both found it independently: I found it from a kind of photographic image of the score in my mind, and he found it by working through the score methodically. After correcting it, the composition proceeded without difficulty. Thus there is something here that cannot be defined: that an organism, it seems, demands certain things, and that we have no other choice than to subordinate ourselves to it intuitively. Is this a question of training, tradition, or habit? Or, are there certain laws of which we are unaware? This is something I have experienced quite often while composing. Once, while writing a violin sonata, I wanted to skip the scherzo but could not. As long as I had not written the scherzo, I could not find anything for the final movement.