Geshe Thubten Palzang
How we ask for directions to a new place is really dependent on whether we really intend to go to that place. Suppose two people asked about the route from Dharamsala to Mangalore in South India. One person might be chatting casually, while the other is actually planning to travel there the next day. Although both people ask the same question, they are looking for different levels of precision in the answer.
For someone who has no real intention of going, a rough answer would suffice, and they wouldn't probe further. However, for someone who must travel alone, such an answer is insufficient. If you tell them, "You must first go to Delhi," they will ask further questions like, "Where do I catch the bus to Delhi? Where do I buy the ticket? How much does it cost? What time does the bus depart? Where do I get off?" Until they are certain they can travel alone, they will have endless questions, and rough answers won't satisfy them.
The same applies to contemplating the topic of "non-self". If you're satisfied with a rough understanding of it, you may not have any confidence in your understanding when facing death. But it will be too late by then to start asking, "Is it real?" If you're only satisfied with superficial answers in normal circumstances, those answers won’t work when it matters most. Therefore, you must carefully contemplate non-self with a serious attitude.
How then to have that serious attitude to contemplate non-self? The key lies in whether you have strong renunciation (determination to be liberated from samsara).
Renunciation is absolutely indispensable because without it, you cannot realize non-self. The reason is that even if you're intellectually sharp, without renunciation, you'll merely stop at investigating non-self superficially without it truly penetrating your heart.
But once heartfelt renunciation arises, along with urgency to be free from suffering (especially when facing death), and after reflecting on the drawbacks of clinging to the self, you are very determined to end self-clinging. Once you have this strong determination, you will naturally investigate non-self sincerely and thoroughly.
(Note: By the same reasoning, strong renunciation is needed for success in other practices for liberation such as the practice of contemplation of emptiness, meditation, pureland practices and so forth.)
