Why do you need to' in this sentence? ("I wouldn't go so far as to say that computers will replace teachers in the near future.")

Question

Example sentence:

I wouldn't go so far as to say that computers will replace teachers in the near future.

Why do you need "to" in this sentence?

Answer 1

As @PaulTanenbaum points out, that's the rule. But that doesn't say why.

The to that occurs before infinitives marks the constituent following to as the verb phrase of an infinitive (uninflected, tenseless) clause. It's part of the for ... to complementizer (a part of speech that the Romans never discovered) which distinguishes infinitives from other kinds of untensed constituents.

• [For Bill to arrive early] was a bad idea.
  (for marks the subject, to marks the verb phrase, and the whole infinitive clause is the subject of was)

• It was a bad idea [for Bill to arrive early.]
  (Extraposition inserts a dummy it and moves the infinitive subject to the end)

The for is usually not present, and quite often the whole subject of an infinitive is missing. But you can always figure out what it is:

• It was a bad idea [to arrive early.] (somebody -- maybe the speaker -- arrived early)
• I want [(for) Bill to arrive early]. (Bill arrives early; many people can use for here)

Infinitives are pervasive and common in many idioms; I could go on for a long time here. But the reason for the to is to mark an infinitive as an infinitive, so you can tell what you can do with it.

Answer 2

Because that’s the idiom. There’s really no better reason than that. One might as well ask why the to is needed in

I want to eat ice cream.

or

What gave you the idea to look under the couch?

Answer 3

With the exception of certain verbs like help — or after modal verbs like can, might, will — to is always needed for the second verb in an expression.

I come to bury Caesar.
I need to eat.
I wouldn't † go to meet... [† no to at this point]

Answer 4

Consider this sentence:

They went as far as London.

London is a place, and it makes sense with far, which literally refers to a distance. The opposite of near.

But far can be used figuratively, and in this figurative use, physical distance becomes an analog for the abstract notion of extreme extent, and the going becomes an analog for an action (of some kind: doing, saying):

   go : far   ::   do or say : something extreme

Going far becomes an analog for doing or saying something extreme.

Now, some more abstract ideas. The action called for by this figurative use, go as far as [action], has to be expressed as a nominal, that is, as something noun-like. London, in our literal example of far, was a noun of place; the action in our figurative use of far must be a pure noun of action.

In English, the marked infinitive, the form with to + bare verb, is a pure noun of action; it can stand as the direct object of a verb or as the subject in a sentence:

I wanted to go but to leave was impossible.

And so we use the marked infinitive:

I would not go as far as to say we were dying of thirst. But we were very dehydrated and feeling lightheaded.

I would not go as far as to throw the mobile phone in the recycling bin when all it needed was a new battery.