Knowing the truth is not a matter of figuring anything out or being convinced of the irrefutable logic which leads to that knowledge. Instead it is a decision about what you want to believe as true. Knowledge is therefore derived subjectively. What we know or claim to believe is that which we think serves our purpose: often to be valued and accepted by those with whom we associate.
You can make that decision personally or let someone else do it for you, the most prevalent method. The consequences of that decision are experienced immediately, not in the hereafter. Your general attitude, the degree to which you enjoy peace of mind, your emotional resilience and maturity, your success in personal relationships, and your overall happiness are a direct result of what you decide to believe as the overarching truth to guide your life.
Too readily people become convinced that truth is some objective, inarguable, concrete reality. One simply has to see the evidence, use correct logic, and the truth is thereby irrefutably derived. Human history demonstrates over and over that such is not the case. Every time what is thought to be true turns out to be false, we are reminded that seeming evidence and human logic are not adequate to determine what is eternally and undeniably true.
Scientific advancement in the last 100 years or so since the advent of the theories of relativity and quantum physics has highlighted the fact that much of what we think we know is not absolutely true. It may appear true in most cases, but there are notable exceptions. Truth turns out to be very pliable. For a time we may believe something true, but don't count on that being eternally so.