A conscious action for the player, yes.
This is where we fundamentally disagree. In my view, the fact that the player is describing what the PC is doing has no bearing whatsoever upon whether the PC is doing something consciously or not.
I get that. I just don't see how you make the leap that because the player makes a conscious decision about what game mechanic to use, the PC must also be making a conscious decision.
So by this logic the PC always does what would be the best thing regardless of what the player describes.
The PC is constantly making knowledge checks, choosing to use power attack (and what amount to remove/apply), etc.
The way you descirbe things the player is merely along for the ride - IMO the game was never designed to follow that path at all.
For example in the games I play in the DM is looking for the player to descibe the PC's actions - he is specifically looking for the player to use words like "carefullly checking" in order to invoke the take 10 mechanic. He is looking for the player to make a description of the PC actions that invoke the take 10 mechanic.
And I suspect this is at the root of our disagreement: is "taking 10" the norm or the exception? Based on your comments above, I think you would say it is the exception, because the player (and thus the PC) has to consciously decide to do it. I, on the other hand, consider "taking 10" to be the norm; it's what everyone does almost all the time when they aren't in unusual circumstances (i.e., threatened or distracted).
And nowhere in the rules does it say taking 10 is the normal. It says it will give you an "average" result, never normal.
That's what I think Chris Sims was really saying in regards to his "house rule" -- that if the players really understood the rules correctly, they'd be taking 10, because that's how the people who wrote the rules intended to model ordinary, everyday skill checks like driving a car around town. They didn't expect players to choose to roll the checks and crash their cars 1 out of every 20 times they get behind the wheel. (If you ask me, those writers forgot two basic principles: most players like to roll dice, and few players read the rules very closely.)
Nope I absolutely disagree.
He specifically made it a house-rule because he thought the same way you do - not because that is how the designers had thought. {That was the real reason I pointed it out - this similarilty in your thinking and the fact that he specifically said it was a house-rule because of it.}
He did it because it made things easier.
He also included the passive scores in his "house rule".
I am also sure that Chris wasn't even part of the "design" group for 3rd ed (which created the take 10 and 20 rules) since per his profile he started working for small d20 companies in 2003 (3rd ed came out in like 2000).
"Chris Sims started out working for small d20 companies in 2003, then landed a freelance editor gig for Wizards RPG R&D. Wizards finally got annoyed enough by his constant applications to hire him as the Duel Masters editor in 2005. From there, Chris wheedled his way into RPG R&D as an editor, and finally became a story designer after masterminding a few choice assassinations. His credits include Monster Manual V, Secrets of Sarlona, Rules Compendium, and the Eberron Survival Guide (thanks, Logan!)."
I still don't think you understand me on this point. What I was attempting to illustrate is that when I am driving "normally," I am doing so carefully/cautiously/conscientiously enough to avoid making simple mistakes (not that by driving normally I can avoid simple mistakes). In game terms, I'm taking 10...because if I wasn't, I'd be rolling my skill checks, which would mean that at least 5% of the time I'd be making a simple mistake.
And what I am saying is that part of your "normal" is a conscious decision to follow your training and not to focus on other things - conversations, cell phone, radios. You would mak a conscious choice to not answer the cell phone while driving, you would make a conscious choice to not turn the radio up too loud, you would make a conscious choice to not do distracting things. It is still a consciouls choice.
If you have lots of driving experience your skill modifier would be much higher than one is is just starting out - so that you would get an success on an average difficulty task without even having to roll (that is a "1" would yield an 10 result. Someone with a low modifier would need to take 10 in order to ensure that they would get a success on an average difficulty task. That is the difference. IMO you are mixing these two things together.