This paper addresses the question of how we can understand reasoning in general andmathematical proofs in particular. It argues the need for a high-level understanding ofproofs to complement the low-level understanding provided by Logic. It proposes a role forcomputation in providing this high-level understanding, namely by the association of proofplans with proofs. Proof plans are defined and examples are given for two families of proofs.Criteria are given for assessing the...