The text of Gaius\u2019 Institutes concerning the price of a sale contains a curious peculiarity. Gaius first of
all reports the requisites of the price in the form of peremptory rules, but soon afterwards he indicates
as consequence (nam...) a contrast of views: some jurists admit the relevance of a sale which doesn\u2019t
observe these requisites. The Author suggest that the (merely) apparent contradiction is an example
of the particular approach \u2018operativo-cautelare\u2019 of the whole work: Gaius wants to point out, in a
\u2018warning perspective\u2019, the conditions to be complied so that the effect of the legal transaction is sure
and beyond dispute, by distinguishing from the case in which the effect is uncertain
