An approach to acquiring justification that transforms why-questions into what-questions, borrowing the power of existing techniques, is discussed. The constrained dialogue has been implemented in an interactive tool, called ASK, that interviews experts and builds programs. The approach is applied to two different knowledge-acquisition problems; the acquisition of diagnostic strategy (why this action is chosen in this situation) and the acquisition of design rationale (why this device is designed this way). Generalization of the justification technique and key open problems in justification elicitation are examined.