One party induces an assumption in the mind of another. Australian law has arguably given expression to three moral duties relating to induced assumptions: the duty to keep promises,the duty not to lie and the duty to ensure the reliability of induced assumptions. This book expounds the third of these duties and shows how it can be used to shape 'equitable' estoppel, a doctrine emerging from the decisions of the High Court of Australia in Waltons Stores and Verwayen. It does not purport to cover the entire law of estoppel, but does examine, analytically, how the doctrine might operate in a series of problematic cases at the edge of contract law.