Sentence:  Mr. P. did not consider that branch, strictly and technically speaking, public revenue; at least it did not arise from taxation, because those persons who had paid this money had received a full equivalent for the same; there was a <WSD>quid pro quo</WSD> on both sides; and this was not taxation, it was a sale; the parties therefore from whom this money was derived had not been taxed.<!-- quote-book 
Meaning of the word marked with <WSD> tags:  An equal or fair transaction or series of process of exchange transactions; tit for tat.