hashkafah philosophy - Where does the sense of morality come from?

Where does our sense of morality which impels us to right conduct come from?

Is it something internal to us, or perhaps it is external to us? Is it physical or spiritual, etc.

For example, does our sense of right and wrong stem from thought, such as thinking about the distress of others (potential or actual) and feeling empathy thereby refraining from doing something which may harm them. Or perhaps it stems from some kind of spiritual sense in us.

Perhaps an explanation of what is the "yetzer tov" would answer this if that is the driving force.