There is faith; there is doubt. In Buddhist practice, we examine the belief and the doubt that we experience in our mind and we see that these two are conditions changing.
I have contemplated doubt itself as a sign. I’d ask myself a question like, ‘Who am I?’ and then I’d listen for the answer – something like, ‘Sumedho Bhikkhu.’ Then I’d think, ‘That’s not the answer; who are you really? I’d see the struggle, the habitual reaction, to find an answer to the question. But I would not accept any conceptual answer. ‘Who is it sitting here? What is this? What’s this here? Who is thinking anyway? What is it that thinks? When a state of uncertainty or doubt would arise, I would just look at that uncertainty or doubt as a sign because the mind stops there and goes blank, and then emptiness arises.
I found it useful to empty the mind by asking myself unanswerable questions which would cause doubt to arise. Doubt is an impermanent condition. Form, the known, is impermanent; not knowing is impermanent. Some days I would go out and look at Nature and observe myself just standing here, looking at the ground. I’d ask myself, ‘Is the ground separate from myself? Who is that who sees the ground?…Are those leaves and the ground in my mind or out side my mind? …What is it that sees? I see the eyeball?…If I took my eyeball out, would it be separated from myself?…Would I still see those leaves?…Are they still there when I’m not looking at them?…Who is the one that’s conscious of this anyway?’
This reflection by Ajahn Sumedho is from the book, The Way It Is, pp. 17, 18.