The basis for drawing rational conclusions about the world – more fundamentally what makes rational thought possible – is the presumption human beings possess knowledge having a high or satisfactory degree of a reasonable probability of truth. (This concept is covered in greater depth in the previous post Certainty Vs Probability. )
If we use rationality as the guide to approach questions in nearly all areas of life, we quickly realize the process required to think and act rationally necessitates a presupposition in knowledge that displays a reasonable probability of truth – not absolute certainty of truth. This is especially true with regard to social and hard sciences. The logic of the scientific method requires its adherents to presuppose there is validity to knowledge demonstrating a reasonable probability it is true; we test hypotheses and design experiments based on their reasonable probability of truth – not an absolute certainty of truth.
The result of employing this belief or concept has worked well, at times resulting in the validation of reasonably probable hypotheses that later provided the basis for reliable theories and scientific laws. The tendency, in academia especially, is a myopic belief that the limited number of such laws and “empirical facts” we have unearthed about the world are grounds to minimize or dismiss other forms of knowledge derived from a reasonable probability of truth.
The belief is often expressed with a careless arrogance. Example: I had an earth science professor in college who was adamant his views about the world were based solely on “facts and evidence provided by science.” He would have been more accurate and believable to claim his worldview was based on knowledge displaying a reliable degree of probability of truth.
Were it possible, we would ideally base the beliefs that comprise our worldview, as well as our everyday thoughts, choices, and actions on “hard facts” and empirical evidence; but the limitation of knowledge provided by scientific inquiry makes that impossible. Any conscious attempt to govern life in such a way would prove to be futile due to the paralysis it would bring with any attempt to put it into action.
Rational people come to a realization they form their worldview based on the degree of reasonable probability of truth our knowledge provides us.
Like most beliefs, claims, and actions in life we can and do draw conclusions, whether consciously or not, about the difficult questions of human life based on the degree of reasonable probability of truth any given form of knowledge provides us. This approach is most rational.