The field of learning disabilities faces a fundamental problem of providing a definition acceptable to a broad constituency. In attempting to explain why this situation exists, we offer arguments based upon concepts from the history and philosophy of science. I t is concluded that learning disability is a victim of its own history, and a breaking from the past is necessary for the definitional problem to move closer to resolution. Few of us take the pains to study the origin of our cherished convictions; indeed, we have a natural repugnance to so doing. We like to continue to believe what we have been accustomed to accept as true, and the resentment aroused when doubt is cast upon any of our assumptions leads us to seek every manner of excuse for clinging to them. -J. H. Robinson