07:46 Jan 22 

its incongruety almost physically. Though, the usage of bare-infinitives without an auxiliary verb in simiar cases seems to be not impossible. What I can see here, that the only thing "to" marker does - it maintains its prepositional value. I tend to rewrite it:'The main thing is - not to give up!'

04:50 Jan 22 

That wouldn’t work. “The main thing is not give up” doesn’t sound right at all.

19:51 Jan 21 

to remove "to" from there:
'the main thing is not give up' - ?

17:46 Jan 21 

I have put "splitting" in inverted commas because it's a misnomer; "to" is a marker, not part of the infinitive itself. But that's what everyone calls it.

All I would say here is that blanket rejection of split infinitives is very unusual in modern English usage guides, and I myself do not subscribe to it. The idea that it is unconditionally wrong to insert anything between "to" and the infinitive originated, or at least was first articulated, in the nineteenth century. Some eminent writers split infinitives; others don't. I myself would certainly say "not to give up" and would not say "to not give up", but there are many cases in which avoiding the insertion of a word between "to" and the infinitive produces a very awkward result.

Even if Shakespeare had been an infinitive-splitter (which he wasn't; it was very unusual in his period), he would not have written "to be or to not be"; the rhythm is all wrong. That is important, I think; this is really a stylistic rather than a grammatical question.

The Wikipedia page on this subject is excellent:
http://en.wikipedia.org/wiki/Split_infinitive

14:45 Jan 21 

When comparing the number of Google hits, one should set 100 results/page and then click on the last/highest page number (displayed at the bottom of the first page). It works in most cases.