Commentaries on the Last Two Titles of the Digest

4. An exception vitiates a Rule, not in total, but only in the case excepted, in this law 1, at the end; Law 1, in the beginning, Digest, On the Rule of Cato. An exception confirms the Rule in cases not excepted, Law 12, paragraph "the same is responded," 43, verse "for he who by this," Digest, On instruction and instruments of legacy; Law "when the praetor," 12, in the beginning, Digest, On judgments. Contrary to Hotomannus in the said place and Freherus, 2, Parerga 13, who deny that the words in this law, which when in some respect it is faulty, it loses its function, are to be referred to Exceptions. But they attribute this opinion to Paulus: since the function of the Rule is to define controversies, if it is distorted and faulty, it never performs its function; with the verses of Lucretius brought forward:

Finally, as in carpentry, if the first rule is false,
It is necessary that all things are done incorrectly and askew.

5. An exception ought to be regarding the Rule, Law "for what clearly," 4, paragraph, final, Digest, On penalty of legacies; as, for example: I give and bequeath all my estates to you, except the Tusculan estate. Every man runs, except Socrates. Contrariwise, a testator would ineptly except thus: I give and bequeath all furniture, except wine. And this exception is foolish: Every man runs, except Titius's horse. Those who interpret Law 1, paragraph, final, Digest, On the Rule of Cato regarding a conditional legacy bump against this thesis: those who read in paragraph 2, Institutes, On actions, certainly not in one case. Indeed, Justinian himself also, or rather Tribonian and his colleagues, Theophilus and Dorotheus, bump against it, while from the rule, Witnesses are to be employed in a testament, with whom there is capacity for a testament, they except the wicked and the intestate, paragraph 6, Institutes, On the ordination of testaments, not comprehended under the rule, because these have neither active nor passive capacity...