....panna underlies all the other aspects of the practice

According to the theory, we say that it's sila, samadhi and then panna; but I've reflected on this and found that panna underlies all the other aspects of the practice. You need to fully understand the effects of your speech and actions on the mind and how it is that they can bring about harmful results. Through reasoned reflection you use panna to guide, control and thereby purify your actions and speech. If you know the different characteristics of your actions and speech which are conditioned by both wholesome and unwholesome mental states, you can see the place of practice. You see that if you're going to cultivate sila, it involves giving up evil and doing good; giving up that which is wrong and doing that which is right. Once the mind has given up doing wrong and has cultivated doing what is right, it will automatically turn inwards to focus upon itself and become firm and steady. When it's free from doubt and uncertainty about speech and actions, the mind will be steadfast and unwavering, providing the basis for becoming firmly concentrated in samadhi. This firm concentration forms the second and more powerful source of energy in the practice, allowing you to more fully contemplate the sights, sounds and other sense objects which you experience. Once the mind is established with firm and unwavering calm and mindfulness, you can engage in the sustained contemplation of form, feeling, perception, thought and consciousness, and with the sights, sounds, smells, tastes, tactile sensations and mind-objects, and see that all of these are constantly arising. As a result you will gain insight into the truth of these phenomena and how they arise according to their own nature. When there is continuous awareness, it will be the cause for panna to arise. Once there is clear knowledge in accordance with the true nature of the way things are, your old sanna and sense of self will gradually be uprooted from it's former conditioning and will be transformed into panna. Ultimately, sila, samadhi and panna will merge in the practice, as one lasting and unified whole. (Ajahn Chah)