In discussing temporal identity, there is a strong temptation to use expressions like 'the bike then' or 'the bike as it was yesterday' or 'the bike as it was at that spatio-temporal moment' - see the comments to my previous post. As though 'the bike then' refers to some different object than 'the bike now' or 'the bike today'.
These expressions don't make any sense to me. Surely 'then' and 'now' or 'yesterday' and 'today' are just adverbs modifying the verb, rather than an adjective modifying a referring phrase or description. Consider
This bike, which was repaired yesterday, has a new mudguard today.
The sentence contains just one subject: 'this bike'. It is modified by two predicates. The first - 'was repaired yesterday' - tells us something that happened at some previous moment to the bike. The second - 'has a new mudguard' - tells us something that is true of it today, now. It makes no sense to divide the subject into something that is or was 'the bike yesterday', and another, different thing, that is 'the bike today'. Both 'was repaired' - which is a predicate in the past tense - and 'has a new mudguard' - which is in the present tense - qualify this single bike. Or 'this bike now', if you really want.
If there really is an object such as 'this bike then', it is an object to which the predicate 'is now being repaired' applies. For it was true to say of the bike, then, 'this bike is being repaired'. By contrast, the past tense predicate 'was being repaired' applies to 'the bike now'. But as I say, modifying a subject expression by means of an adverb doesn't make sense.
The medieval writers keenly appreciated this. A noun or referring phrase has no tense attached to it. Its semantics does not include time. The sense of time is what a verb brings in. Hence past, present and future tenses, and hence qualifying adverbs like 'now' and 'then'.