Of true knowledge at any time, a good part is merely...

Of true knowledge at any time, a good part is merely convenient, necessary indeed to the worker, but not to an understanding of his subject: One can judge a building without knowing where to buy the bricks; one can understand a violin sonata without knowing how to score for the instrument. The work may in fact be better understood without a knowledge of the details of its manufacture, of attention to these tends to distract from meaning and effect.