All Harry could think of doing was to keep Quirrell talking and stop him from concentrating on the mirror.
(Harry Potter and the Sorcerer's Stone)

In a different phrase containing all and do, I see the infinitive complement starts without to. Is it the same when do is replaced from doing, or is the infinite marker required in the latter case?

1 Answer 1


The explicit to marking the infinitive is actually somewhat "optional", though idiomatically it would probably be used more often than not in OP's exact context.

But there's no grammatical reason why All Harry could think of doing is any different to, for example,...

all I can do is watch (5690 hits in Google Books)
all I can do is to watch (3940 hits)

Not only could the to reasonably be omited in OP's case - it could be recast as

All Harry could think to do was [to] keep Quirrell talking.

As regards ...and stop him..., it's just a stylistic choice to discard the optional to the second time. But I must admit it would be very unusual (and perhaps "ungrammatical") to use it only for the second verb. Besides, in this exact context, that and could probably be replaced by in order to, so stopping Quirrell concentrating doesn't quite have the same relationship to Harry's thinking as keeping Quirrel talking.

  • 2
    Strange! Counting the results on your second link, I only get 26 results (click through to page three and the number drops from 3940 to 26), and discarding duplicates I only see about 15. Doing the same with the first link, I find an order of magnitude more results. That's more in line with my expectations, but I'm not sure how reliable this data is... GloWbE gives 14 and 0 results respectively, for what it's worth.
    – user230
    Commented Aug 15, 2013 at 3:46
  • @snailboat: You're quite right. I thought the figures for that to were surprisingly high, but I didn't bother to check in detail. It doesn't really affect my substantive point though - it does occur, and I don't see it as "grammatically incorrect". It's just less common to include to in my exact example (but I'd be prepared to bet the idiomatic preference is precisely opposite for OP's exact example). Commented Aug 15, 2013 at 14:04

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