As I have said previously, if the only evidence being considered is limited to scientific knowledge of material properties and reactions, you are bound to come to a materialistic conclusion - but such a conclusion will fall far short of an explanation.
And, as has I have pointed out, if you want to consider something other than evidence produced and interpreted under the scientific method, you need to justify it. As an annexe to that point, it's that science is limited intrinsically to 'material' considerations, it's that science is limited to measurable phenomena - if you have something non-physical that has a measurable effect, then science will accommodate it; what you have, though, is something alleged which has no apparent visible effects, at which point you have to ask what the justification is for considering it.
The current paradigm doesn't fall short of an explanation, it provides an explanation that you - for ideological reasons - don't appear content to accept. If you want to claim that it's not a viable explanation you need to show which of the steps is in error, and claims of hypothetical untestable 'other' forces is not sufficient to reject that demonstrable evidence we do have.
because we sometimes choose to give in to temptation instead of following our conscience
But surely, if we have freedom to consider, then we won't fall prey to temptation, because we can freely consider the options and understand which are the negative choices?
Most people acknowledge the reality that they have conscious control of their thoughts, words and actions, which is why they can justifiably regret that they may have miss-used their power to control.
Most people believe they have conscious control of their thoughts, I'd accept, but most of them haven't considered that assumption in any depth to understand whether they are correct in their assumption. Many people can also be wrong, as is evidenced by (amongst others) the existence of Abrahamic religions and Hinduism, and the fact that Donald Trump is US President.
As stated above, your restrictions on admissible evidence would automatically rule out any non physical cause.
And, as stated above, science doesn't rule out non-physical causes, it just doesn't have any mechanism for interpreting allegations of causes with no consistent or detectable effects - if you want to posit things outside of science's remit you have to also posit a system by which those claims can be validated or refuted; logic is one, that falls over pretty quickly on free will, so you need something else.
But if any philosophical contemplation was entirely driven by uncontrollable physical reactions I can't see how any credence could be attached to the result.
Credence in what sense? If my brain detects a drop in blood sugar and a largely empty stomach on a subsconsious level, am I only hungry after i've consciously decided so? Or am I hungry, and then I become consciously aware of that hunger after my brain has processed the fact?
I do not believe the concept of meaning could ever come into our human awareness if there really was no meaning in life.
And you're perfectly entitled to that belief, but I'm under no obligation to agree with you purely on the basis that you have a belief. We see that people have an understanding of 'meaning', and yet it's far from demonstrable that there is an underlying purpose to life. You might not be able to envision the mechanism by which it comes about, but I can't see how it can be impossible to think we could determine meaning in our activities that are not the product of some larger purpose.
O.