What's with 'God bless you'?

The other day my husband asked me why people say 'God bless you'. Isn't 'bless' the form you would use for first person ('I bless you') or second person ('you bless me') only? Why isn't it 'God blesses you'? I explained it to him and he suggested I write a blog post about it, in case others wondered the same thing.

It turns out many others have wondered the same thing, as you can see on this Wiki Answers post, this one on English Forums, or this one on English Language and Usage Stack Exchange.

Image from 'Fields of Cake' blog

'(May) God bless you' is a bit like (or belongs to the same paradigm as)

God save the Queen (not saves)

Long live the king (not lives)

Heaven help us (not helps)

God be praised (not is praised)

So be it (not is)

Truth be told (not is told)

If I were you (not was or am)

The fancy technical name for this kind of construction is 'subjunctive mood'. It's a particular form of the verb, although in English it nearly always looks exactly like the 'normal' indicative form. That's why we don't really recognise it when we see it and why it looks or sounds a bit weird if you think about it.

It's different in meaning from the indicative because it expresses a degree of doubt or wishfulness, or something of a hypothetical nature.

Here are the paradigms for indicative and subjunctive, to compare the differences:

Indicative:

I save

you save

he saves

We save

you(se) save

they save

Note that the only one that is different is 'he saves' (third person singular form)

Subjunctive:

I save

You save

He save

We save

You(se) save

They save

Now the verb form is the same across the paradigm, and it's only the third person singular form that is different from the indicative. You can of course read the Wikipedia explanation of subjunctive mood for more information on this. But that's the general gist of it.