OK, so given we can all agree it's not possible to know EVERYTHING, what exactly is it that is actually informing our decisions?
Perception. Which in turn is converted into something I will call "personal truth" which in turn informs our decisions.
e.g. you perceive a chair, you generate the assertions "a chair exists. It is in this room".
I'm not saying that personal-truth is truth. Truth is usually understood as some sort of global concept. Absolute-truth if you will. The connection of personal-truth to absolute truth is off-topic.
I would posit that if it is rationality, then full information/context is needed in order to draw a conclusion.
It seems that your definition of "rationality" is based on absolute-truth rather than personal-truth? If so, I will agree that such rationality, let me call it absolute-rationality does not exist, because nobody knows absolute-truth.
And as you say, therefore something else is guiding our decisions.
That something-else I shall call personal-rationality. As a result of personal-truth, no full information/context is needed in order to draw a personally-rational conclusion.
OK, sure, but what exactly does it mean to be "more rational?" As I see it, being rational is rather black and white - either you are rational or you are not. Don't see a whole lot of room for play with this since being rational hinges on being objective and impartial.
Yes, it is black&white, except the rational answer is not always a certainty.
e.g. Just like when calculating the expected outcome of a coin-flip, we end up with a certain 50%. The concepts "certain" and "50%" in that sentence are not in contradiction with each other. "Certain" is the black&white part, while "50%" is the rational answer.
What would be the implications of this?
The implications of not having absolute-rationality is that what is rational can differ from person to person or even from time to time. As new information comes in, as your priorities shift, the calculation of what is rational will yield different results.
You can call the new decision "more rational" if you want, though, it's just an expression.
The idea I am trying to put forth is not solipsism or the antithesis of rationality necessarily. So what is left if we neither indulge ourselves of the whim of rationality or solipsism? Is there truly no other way? What does bias have to do with this? If bias is the paradigm by which we live, would it not be better to adhere to such a thing, being aware that it exists and is influencing our behavior? What is the answer? Tell me.
The bias lies in the catalog of personal-truths that a person collects over their lifetime as fuel for their personal-rationality. These personal-truths include perceptions(beliefs) as well as goals.
Yes it pays to be aware of one's own bias. Without such awareness, a person will likely miss the chance to expand/update their catalog of personal-truths when it's important = when such update has a substantial effect on the success of one's own rationality and life choices.