Dear teachers and friends,

I notice that many people use this sentence “what did you do”.

As far as I understand, did is a past tense and do is present tense. How come these two mixes together?

I also would appreciate if anyone can enlighten this more.

Thanks in advance
Do is an infinitive in the sentence, not past tense. The infinitive is used because of did. As English has only a handful of verb forms, the same form can be used in a number of ways. Examples:

Do it now! (imperative)

I do it every day. (present tense)

Can you do it for me? (infinitive, present infinitive, to be exact)

She demands that he do it right away. (present subjunctive)

You need to revise the rules of formation of interrogatives, my friend.

The original sentence is: He did something - the verb is in the past tense.

Since the verb 'did' is not an auxiliary verb, but a notional verb, you need an auxiliary to from a question - the past auxiliary is 'did' (this is, perhaps, the point which confuses you):

What did he do? - the did-auxiliary indicates the past tense, and the verb 'did' in the original sentence becomes a bare infinitive 'do' in the question. Infinitives are not marked for tense, so you shouldn't say that it is present.

Respectfully, Gleb Chebrikoff
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Gleb_Chebrikoff Infinitives are not marked for tense, so you shouldn't say that it is present.
They are marked for tense and even for voice. Fortunately for us students English has only two infinitives. Some non-native grammarians call them the first infinitive and the second infinitive but I don't remember seeing British or American grammarians using those names. Examples:

Present active infinitive: He would do it.

Perfect active infinitive: He would have done it.

Present passive infinitive: It would be done.

Perfect passive infinitive: It would have been done.

This quotation is from A Practical English Grammar for Foreign Students by A. J. Thomson and A. V. Martinet:

"The perfect infinitive is formed with the infinitive of have and the past participle:

e.g. to have worked, to have spoken"

Thank you, Cool Breeze, for weighing in on that question. However, I cannot agree with the viewpoint you have expressed.

According to Sir Quirk et al., there are five criteria for determining whether the phrase (or, in our case, the verb) is finite or non-finite, namely:

a) occurence of VPs in independent clauses;

b) having tense contrast - the distinction between present and past tenses: He is a journalist now. vs. He worked as a travel agent last summer.

c) person concord and number concord;

d) finite VPs contain, as their first or only word, a finite verb form (operator/simple present/past form) + Do support is used for negatives and interrogatives.

e) mood

We are particularly interested in number 2, and, by following the link below, we shall clearly see that infinitives do not have tense distinctions:

Non-finite VPs have no tense or mood distinctions. Here is yet another proof:

Infinitive is a non-finite form of the verb

Non-finite forms of the verb have no tense distinctions


Infinitive has no tense distinctions

There are forms used to refer to particular moments in time, but, as we know, time and tense differ.

Respectfully, Gleb Chebrikoff
This is a matter of varying terminology. Every grammarian whose books I have read has given a name to the two infinitives English has, and native speakers use the terms present and perfect infinitive in the active and passive voice. One of these people is perhaps the best-known American grammarian George O. Curme in his Syntax (Chapter XXIII). I'll stick with that bunch, if you don't mind.Emotion: wink

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I surely don't, CB!

I suppose we are talking about slightly different subjects. Please, tell me:

do you agree with the statement that the infinitive, as a non-finite part of the verb, has tense distinctions?

I don't. What is your take on it?

As I now see, some of the most trusted textbooks for foreigners, such as the one written by C. E. Eckersley, give the following table for the infinitival forms:



(to) write

(to) be written

(to) have written

(to) have been written

Voice distinctions +

Aspect distinctions +

Tense distinctions = stumbling block

If 'present' becomes 'simple', things will get more simple! Distinction is where we have things of a similar kind opposed to each other, e.g. present vs. past, but here... Is it present vs. perfect? If so, present is tense, but perfect is aspect.
Gleb_Chebrikoffdo you agree with the statement that the infinitive, as a non-finite part of the verb, has tense distinctions?
I have a pragmatic attitude to language and I like to have a name for grammatical forms. It would seem to me that what I and all the grammarians I am familiar with call the perfect infinitive indeed usually refers to the past:

I would have gone there yesterday.

The present infinitive, on the other hand, usually refers to the present moment or the future:

I would go there tomorrow if I had time.

However, logic doesn't always apply in English, and the perfect infinitive can refer to the future:

He will have solved all his problems by next year.

This isn't surprising since very often even the active and passive infinitives are interchangeable in English:

The chicken is ready to eat / to be eaten.

With the active infinitive the chicken may of course do the eating!Emotion: smile (English isn't the most exact of languages.)

I suggest you use your terms and I use mine. I am sure the vast majority our non-native learners of English have learned a name for the infinitives if they have been taught any grammar at all.

There is nothing for me to argue about in your last post, Cool Breeze. In fact, our views coincide in many respects. As you have said, we should stick to our terms. You call present infinitive what I call simple infinitive (keeping in mind that 'present vs. past' dichotomy is impossible), there is nothing inherently flawed about that.

Tastes differ, so here:


Infinitives are not marked for tense, so you shouldn't say that it is present.”
They are marked for tense and even for voice.

--- they differ, too, although A comprehensive Grammar of the English Language (Quirk...) and Cambridge Grammar of the English Language (Pullum...) hold they are still unmarked, and this is just a fact for our learners to be aware of.

On the whole, I believe that discussions of the kind and quality we hold here are beneficial for anyone taking time to read and understand.

Emotion: shake hands

Respectfully, Gleb Chebrikoff
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