This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
Pure non-disclosure, as the name implies, is the omission to disclose to the adversary party facts not known to him but known to the party so omitting to make disclosure. It differs from fraud and misrepresentation in that the party omitting to make disclosure does nothing in pure non-disclosure by word or act to mislead the adversary party. While in many respects analogous to mistake, it differs therefrom in this: in pure mistake, the adversary party is not aware of the existence of the mistake, in non-disclosure, he is. It must be conceded, however, that many of the cases classed under mistake are really cases of non-disclosure. Active concealment is a form of fraud and is discussed in connection therewith.1