“If you light an oil lamp for the purpose of viewing a picture in the middle of the night, you will see the depictions very clearly if the lamp is both very bright and undisturbed by wind. If the lamp is not bright, or is bright but flickering in the wind, then you will not see the images clearly. Likewise, when looking for the profound meaning, you will clearly see reality if you have both the wisdom that unerringly discerns the meaning of reality and an unmoving attention that stays as you wish on the object of meditation. However, if you do not have wisdom that knows how things are – even if you have a non-discursive concentration in which your mind is stable and does not scatter to other objects—then you lack the eyes which see reality. Hence, it will be impossible to know how things are no matter how much you develop your concentration. And even with a perspective that understands reality – selflessness—if you lack a firm concentration that stays one-pointedly on its object, then it will be impossible to clearly see the meaning of the way things are because you will be disturbed by the winds of uncontrollably fluctuating discursive thought. This is why you need both serenity and insight.”
From The Great Treatise on the Stages of the Path to Enlightenment: The Lam Rim Chen Mo by Tsong Khapa. Translated by the Lamrim Chenmo Translation Committee. Snow Lion/Shambhala Publications.