This section is from the book "Popular Law Library Vol7 Equity Jurisprudence, Trusts, Equity Pleading", by Albert H. Putney. Also available from Amazon: Popular Law-Dictionary.
"This division embraces those cases in which a transaction, although it may be perfectly regular in its external form, is valid perhaps by the original rules of the common law, is impeachable in equity because it lacks that absolute consent which is regarded as essential by courts of equity. The equitable conception of true consent assumes a physical power of the party, an intellectual and moral power, and that he exercised these powers freely and deliberately."6
This division is subdivided into transactions void or voidable with persons totally or partially incapacitated, and transactions presumptively invalid between persons in fiduciary relations.
The various classes of persons whose contracts are void or voidable have already been discussed under the subject of contracts.7
In such cases equity will grant relief by ordering the cancellation of the contracts, which is in many cases a much more effective remedy than any which can be obtained at law.