what is sought; the induction is therefore incomplete. This is especially so because the cause of the judgment in the primary case may consist of shared attributes together with other attributes, all actually present in that case. When the shared feature is present in the primary case, the judgment holds because its cause is complete; when it is absent, the judgment ceases to hold because the cause is incomplete. It therefore does not follow that the presence of the shared feature in the secondary case establishes the judgment, since the remaining attributes, or some of them, may be absent.

“As for ‘division and elimination,’ it amounts to claiming that the attributes of the primary case are confined to a specified set, then ruling out all but the one retained. This, too, does not yield certainty. The judgment may hold in the primary case because of the very nature of that case, rather than because of something extrinsic; otherwise, an infinite regress would follow. Even if it holds because of something extrinsic, it always remains possible that this is something other than the enumerated attributes, even though inquiry has failed to uncover it. Matters of ordinary experience are different: when our sight is sound and nothing obstructs it, we have no doubt that there is no sea of mercury or mountain of gold before us if we do not see one.

“Even if the possible causes are confined to the enumerated attributes, the judgment may be explained by all of them together, or by some that are not present in the secondary case. The presence of the judgment alongside the shared feature in a particular case, despite the absence of other attributes accompanying it in the primary case, does not establish that this feature alone accounts for the judgment. In that particular case, the judgment may have another cause, and there is nothing impossible about this. Even if it has no cause other than the shared feature, that feature may be a cause by virtue of its particular character rather than its general nature. If it is demonstrated that the attribute entails the judgment by virtue of its general nature, then—quite apart from the difficulty of establishing this—reasoning by analogy becomes unnecessary.”