The question is, what is “the truth”. Science comes closest, at least in truth that is logical and based in fact. Biological sciences, the life sciences, are especially useful. The myths of old answered our questions until science came of age. Myths were as close to truth as we could get.
I suppose Buddha’s Four Truths are a mix of both science and spiritual truth. His Fourth Truth, “There is salvation for him whose self disappears before truth” is a little puzzling until you nail down what “truth” might be. For me, the first three of his truths offer observations that zero in the overall truth that addresses the human condition quite scientifically, i.e., rationally, empirically, verifiably.
The hitch here lies in the impossibility of teaching anyone truth. Like beauty, truth is in the eye of the beholder. The only thing that really makes spiritual truths worth contemplating seriously is the fact that these truths have been providing useful answers to generations of people. The test of time is a most accurate test. That said, it is also important to read between the lines, so to speak, to find the kernel of truth that jumps out at you.
The kernel of truth that jumps out at you is actually what you already know intuitively but for which you have yet to find words. The idea that nothing true can be seen without looking within is more a spiritual truth. I don’t see any way to prove it other than through personal experience, which means looking within.
The necessity to look within for truth is especially difficult to achieve because we are such a social species. We are so easily influenced by the viewpoints of others. This Hidden Brain report sheds light on this: Researchers Examine When People Are More Susceptible To Fake News. (You may think of “fake news” as anything less than experience tested truth.)