Can an oral agreement be rescinded if it is not in writing?

In Phipson on Evidence (12th Ed.), at para. 1916, it is stated as follows: “A contract required by law to be in writing may, whether before or after breach, be wholly rescinded by an oral agreement ... but it cannot be partially abandoned or varied thereby ... The question of rescission or variation is one not of law, but of fact, to be determined by the intention of the parties, which may be either express or implied Various cases, including Morris v. Baron (supra), constitute authority for the above proposition.