Over the more than three decades of my life as a physician, I have been constantly amazed at how subtle and elegant nature is as a teacher. Our questions to her, though, must be clear and unambiguous. Otherwise, the answers we receive are likely to be misleading and confusing. As I have matured as a clinician, I have tried to improve my questions to increase my chances of receiving an answer. For the past decade, I have been pondering the subject of strabismus with which I have busied myself for practically two and one-half decades. I began to realize that my time, my share of wisdom, my abilities to carry out the prodigious work necessary to create a book out of nothing but thought, reading, and reflection on the work of others, as well as my own experience, were perhaps becoming limited. I do not doubt that they will become even more limited! Thus I have been led to write this book. Further, I am left in greater awe of prolific writers, particu larly those who write with the precision and attention to detail necessary for a medical text. Let me warn the reader at the outset that my approach in this book is "teleologi cal. " I am well aware of the conflict between science's notion of causality as only local and instrumental as opposed to the anthropomorphic notion of purpose or design in nature implied by the choice of this teleology.