 Communication with others requires that ideas be expressed with words. Complex thought and the accumulation of personal knowledge are also hardly possible without recourse to words. Thinking and expressing thought with words with insufficient care, however, are the main sources of error. Much thinking takes place with exclusive attention to words without regard for the ideas signified by those words. It is also common for the association between words and ideas to drift in ways that damage the coherence of thought. The priority of thought to linguistic expressions is put in extreme terms.