Take heed ere it BE / IS too late

Question

Can generalised form of is that is be be used everywhere?

Are the following two sentences different?

1. Take heed ere it be too late.

2. Take heed ere it is too late.

Answer 1

1. Take heed [ ere it be too late. ]
2. Take heed [ ere it is too late. ]

They're only different in that in the former (enclosed in square brackets) is a subjunctive content clause governed¹ by the preposition (in bold), and the second is a declarative content clause.²

There is no appreciable difference in meaning between the two sentences, although the former one implies that it being too late is less likely than in the latter. (Maybe a native speaker could confirm this.)

With respect to current usage, ere isn't very common (and hence the constructions in which it occurs aren't either). Dictionaries like LDOCE, the ODE, and Merriam-Webster label it as literary, old-fashioned, archaic.

The Google Ngram Viewer gives us the following chart:

From this chart we can glean that both occur approximately equally infrequently nowadays.

I'd recommend you not use either of them in any register, unless you're writing a novel and know what you're doing, and/or are trying to evoke an old-fashioned sort of feeling surrounding ere and other such (antiquated) vocabulary items.

As far as the difference between the two goes: the subjunctive is generally seen as old-fashioned (esp. in BrE, but not as much in AmE, I think) / stilted / formal (though this depends on the construction), and might be perceived as such in this one, but if you're already going for a literary, etc. mood, you might as well prefer it to the non-subjunctive clause.

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¹ I take for granted what user tchrist posits in this answer, comparing ere to lest, etc.

² See The Cambridge Grammar of the English Language (2002) by Huddleston et al. (CGEL), p.1000, which gives an overview of such subjunctive clauses in Present-day English – it doesn't specifically name ere (but it does lest, etc., and see footnote 1 for that).

Answer 2

In these examples, "is" is in the present tense, "be" here is infinitive so, yes they are different.

One should use "be" here, because the following question and answer would not make sense in the present tense:

(is)

• Q: "when will it be too late?"
• A: "erm... now, I guess". So... no point in taking heed, it's already too late.

(be)

• Q: "when will it be too late?"
• A: "Not telling you, but soon". Ok, guess I better take heed, because bad things could be coming any minute but not exactly this very second.