Yes, yet another philosophy thread...

The subject of selfishness was raised in Sasaki's thread, which is a topic that always interest me. Now, my thesis is as follows:

All our actions happen for a reason. I am not talking about a rational reason, just that it happens because of something. Now, all our actions are triggered by electric impulses from the brain and some claim all our actions to be impulsive, but let's not get caught up on that, the point is: what triggers these impulses?
There must be a reason why our brain tells us to do certain things, and that reason must, in my opinion, be plain and simple egoism. Everything we do, every step we take etc. is done because our brain consider this to be good for us in some way, consiously or subconsiously. I'll take a few basic examples to prove my point that everything we do is done for an egoistic reason.

1. You buy yourself a coffee (assuming that you like coffee).

It's quite obvious. You enjoy the taste of coffee, it gives you energy, it's nice and warm and so on.

2. You buy your friend a coffee (assuming he/she likes coffee).

Consiously, most people do this to be nice, but in the long run, your brain is aware that this favour will earn you a favour in return, and moreover, this act will be appreciated by your friend who will be keen to you. Also, the sheer pleasure of feeling like you are a nice person is a positive effect that your brain strives after.

3. You buy a complete stranger (who you've not even spoken to) a coffee.

About the same as above, you will probably not get a favour in return, and you can't know if this person enjoys coffee, but you've done something nice, which will make you feel good about yourself. An alternative is that you would do this for your own amusement, as it's quite odd to hand coffee to strangers.

I think this theory is applicable to pretty much every situation, and from my way of seeing things, everything we do means we're being egoistic, thus I'm not condemning egoism as something entirely negative. But maybe I'm just cynical, what do you think? Discuss.