Marshall McLuhan was the master of the cryptic aphorism, or 'probe', and believed that the secret of perception lies in the power of words to either sharpen or dull the senses. He reveled in metaphor, allusion, implication and intimation and used probes to compress many of his complex and visionary ideas into a few thought provoking words; posing a new question interested him far more than confirming an idea. His probes push the participant into completing...