I have never understood this. It works this way for find/found, grind/ground, and others. Why is it not mind/mound?
Learn English – Why is the past tense of “mind” not “mound?”
past-tense
Related Solutions
As you've noted, rather than is a bit of a strange beast. I can't offer a complete analysis, but it isn't grammatical to put a finite verb after than in the past tense. Rather, it must be either the uninflected base form or the present participle. The choice between them is partially controlled by the tense of the main verb.
He left rather than watch the movie.
? He left rather than watching the movie. (Sounds wrong to me)
*He left rather than watched the movie. (Always wrong)
From this article, I offer the following quote from the American Heritage Book of English Usage:
The phrase rather than consists of an adverb and a conjunction and often means “and not,” as in I decided to skip lunch rather than eat in the cafeteria again. It is grammatically similar to sooner than in that it is used with a “bare” infinitive—an infinitive minus to: I would stay here and eat flies sooner than go with them.
Rather than can also be used with nouns as a compound preposition meaning “instead of”: I bought a mountain bike rather than a ten-speed. But some people object to this use, insisting that than should be used only as a conjunction. They therefore object to constructions in which rather than is followed by a gerund, as in Rather than buying a new car, I kept my old one. [Editor's note: these people are clearly insane. rather than + gerund is just fine, as is rather than + noun phrase.]
In some cases, however, rather than can only be followed by a gerund and not by a bare infinitive. If the main verb of the sentence has a form that does not allow parallel treatment of the verb following rather than, you cannot use a bare infinitive, and you must use a gerund. This is often the case when the main verb is in a past tense or has a participle. Thus, you must say The results of the study, rather than ending (not end or ended) the controversy, only added to it. If the main verb was in the present tense (add), you could use the bare infinitive end.
Curiously, when the rather than construction follows the main verb, it can use other verb forms besides the bare infinitive. Thus you can say The results of the study added to the controversy rather than ended it.
The overriding concern in all of this should be to avoid faulty parallels, as in sentences like Rather than buy a new car, I have kept my old one and Rather than take a cab, she is going on foot.
If I found a ball in the morning, I might say in the afternoon I found a ball today. The past tense locates an action at a specific time in the past, but today is a sufficiently prolonged period of time to allow the use of the past tense on the same day. I have found a ball today could occur, but only exceptionally, because the perfect construction is not normally used when the sentence contains a specific time reference.
I find a ball today would be found only rarely and then only in a hypothetical sentence such as: Let’s suppose I find a ball today.
Best Answer
Find and grind are strong verbs that inherited Proto-Indo-European ablaut. They have been verbs for a very long time.
Mind is a weak verb. The Oxford English Dictionary describes its origin as "Formed within English, by conversion". In other words, the noun mind came first, and the verb mind was derived from the noun. Verbs that are derived from nouns cannot be strong verbs (unless they are altered by analogy). In fact, there is no productive way to derive new strong verbs. They're pretty much all inherited from at least Proto-Germanic verbs (I don't know, there might be a few that come from other sources).
This information is of limited usefulness for determining the conjugation of any particular verb, since often it's hard to tell if an English verb is derived from the corresponding noun, or vice versa (for example, grind and find also exist as nouns, via conversion/zero-derivation from the verbs).