If I hold my head to the left and look down at the handle grips and front wheel and map carrier and gas tank I get one pattern of sense data. If I move my head to the right I get another slightly different pattern of sense data. The two views are different. The angles of the planes and curves of the metal are different. The sunlight strikes them differently. If there’s no logical basis for substance then there’s no logical basis for concluding that what’s produced these two views is the same motorcycle.
Robert M. Pirsig, Zen and the Art of Motorcycle Maintenance: An Inquiry Into Values