Question II. Why is Achan's genealogy indicated so carefully?

The Jew Rashi says it was done to signify that that had at last come to pass which had been shown at Zerah’s birth, when — as he was just about to be born, and was putting out his hand from his mother’s womb — the midwife bound a scarlet [thread] on him (Gen. 38:28): namely, because from his descendants there was to be one who would steal a scarlet garment, and give much [occasion of] public mourning. But this, says Abulensis (q. 4), “is ridiculous, since it is established that the scarlet was placed on the hand of that [child] about to be born for another cause.” But of the same effect there are sometimes not one only, but many causes. And what forbids [that] this too was one of the secondary, as it were, and more hidden causes? The midwife did not indeed look to this, nor purpose in her mind, that Achan should [one day] be made famous by any scarlet theft; but how many things does the Lord do and show through men who know [it] not? [He] who (John 11:50 [printed “Ioann. 27”]) said, “It is expedient for us that one man die for the people, that not the whole nation perish” — did not say [it] of himself (v. 51, in the same place). This [reason], then, can be maintained. Yet there are others more principal and more certain. First: that this Achan might be distinguished from others, if any perchance bore this name, whether in the same tribe or in others. For the community of name, of crime, and of disgrace ought to bring [a community of shame]. There was indeed afterward one Hacan, who wrote a book on the laws and rites of the Karaites and the Sadducees; and of him one of the commentators on Avoth [Pirkei Avot] says: “Let his name be blotted out, like Achan’s.” Secondly: in that inquiry for the guilty one which had afterward to be made, one had to proceed by tribe, by family, and by house; and so Achan was detected. Rightly, therefore, are his tribe, family, and house at once described. Thirdly: that a certain contagion, as it were, of disgrace might be transmitted to the parents and forefathers — [now] long dead, it may be — and be carried, as it were, up or back. And this, first, because sometimes it is partly their fault, in that they too negligently educated [their] sons and grandsons. Secondly: the fear of a common stain and mark of this kind rouses [them], so that all labor in this — that no one in the whole house, stock, tribe, and nation may ever be impious, sacrilegious, [or] criminal. For hence [come] those exhortations, or complaints: “Beware lest you brand any disgrace upon our stock.” “And do you dare to defile such parents, so noble and illustrious a house, so great and ancestral ornaments of the family, with those crimes of yours?” So it is: “A wise son makes a father glad; but a foolish son is the sorrow of his mother” (Prov. 10:1 [printed “10, v. 4”]). Fourthly: that the infamy of the sinner may be increased — [him] whom so good a stock, so honorable a family, so illustrious parents did not recall from the crime. “They dishonor,” says the Lyric [poet, Horace] (bk. 4, Ode 4), “their good birth by [their] fault.” Fifthly: that there may be a kind of solace, as it were, to the most honorable families, when they see that it has always been so from of old — that in a great and excellent house there sometimes exists someone degenerate and infamous. Only care must be taken that not more [such] exist — nay, that not even that one such should have come forth through sloth, indulgence, and the depravity of [his] upbringing. Otherwise [there is] that well-known [saying]: ἡρώων ἀνδρῶν τέκνα, πήματα [hērōōn andrōn tekna, pēmata, “the children of heroic men [are] calamities”]. And [that] which Demosthenes complained of: ἀνδρῶν ἀγαθῶν φαύλους ἀποβαίνειν τοὺς υἱούς [andrōn agathōn phaulous apobainein tous huious, “that the sons of good men turn out worthless”].