ABSTRACT
Certainty and science by definition are never the same thing. The orthodox version of the biology of human twinning is founded on pillars of ‘common knowledge’, falsely and passively simplified by neglect of attention and curiosity. That foundation serves as the basis from which neophytes and veterans alike begin and continue investigations with the best of scientific intentions. Most of the fundamentals of the common knowledge of human twin biology are supported only by repetition, rather than the repeatable-or-refutable observations essential to scientific credibility. These unquestioned answers, taken on faith to bridge the void of ignorance, are not the stuff of science. They may appear serviceably plausible ad hoc, but are worse than useless because they disguise unanswered questions with the false certainty of unquestioned answers. Whereas most other chapters in this volume offer coherent packages of what their authors have come to believe they know, this one is about the difference between not knowing and not being able to learn because things we think we know already prevent further learning.
