One way of knowing is through the study of various teaching from people who have direct experience. This creates a skillful understanding, which is the essential starting point for any task. This is even more true in the realm of spiritual practice since all meditative experiences are translated into the worldview we currently inhabit. We call this "philosophical reorientation".
The other way of knowing is through our own direct experience. This is where it all comes together, and meditation is the ideal technique for examining and integrating our lives. We call such a direct, experiential, and life-changing experience a "genuine insight".
Over time, we have come to learn that meditation with an incorrect understanding not only limits our insight but can lead to suppression of feelings, rigid self-identification, ego-inflation, mania, and spiritual materialism. Conversely, meditation with a skillful understanding can provide fertile ground to realize the potential wisdom, compassion, and contentment already present within the human being.
Direct experience of this deeper truth lies at the core of Zen.