Institutio Oratoria

Now though, for reasons already mentioned, it is most undesirable that he should hunt for and try every single one of those, while actually engaged in pleading his case, it is most necessary in the preliminary study of the case to leave no stone unturned to discover the character of the persons involved, the circumstances of time and place, the customs and documents concerned, and the rest, from which we may not merely deduce the proofs known as artificial, but may also discover which witnesses are most to be feared and the best method of refuting them. For it makes a great difference whether it be envy, hatred or contempt that forms the chief obstacle to the success of the defence, since of these obstacles the first tells most against superiors, the second against equals, and the third against those of low degree.