Every fact is material which is essential to the plaintiff's cause of action or to the defendant’s defence – which they must prove or fail. Every statement which need not be proved is immaterial and should be omitted. The question whether a particular fact is or is not material, depends mainly on the special circumstances of the particular case. Sometimes it is material to allege and prove that the defendant had notice of a certain fact; at other times it is sufficient to aver that he did some act, without inquiring into the state of his mind at the time. In some cases the defendant's intention is material; in a few cases his motive. Sometimes it is necessary to give details as to time, place, or pedigree.
Encyclopaedia of the Laws of England, A. Wood Kenton, 1898, Vol.X, p. 116