There is a certain minimal metaphysics one needs to assume if one is to pursue meditation as a spiritual practice, as opposed to, say, a relaxation technique. You have to assume that mind is not exhausted by 'surface mind,' that there are depths below the surface and that they are accessible here and now. You have to assume something like what St Augustine assumes when he writes,
Noli foras ire, in te redi, in interiore homine habitat veritas. Do not wish to go outside, return into yourself. Truth dwells in the inner man.
The problem, of course, is that few if any will assume that truth dwells in the inner man unless they have already experienced or sensed the self's interiority. For the intentionality of mind, its outer-directedness, conspires against the experience. Ordinary mind is centri-fugal: in flight towards objects and away from its source and center. This is so much so that it led Jean-Paul Sartre to the view that there is no self as source, that conscious mind just is this "wind blowing towards objects," a wind from nowhere. Seeking itself as an object among objects, centrifugal mind comes up with nothing. The failure of David Hume's quest should come as no surprise. A contemporary re-play of this problematic is found in the work of Panayot Butchvarov. The Bulgarian philosopher takes the side of Hume and Sartre. See my Butchvarov category.
Ordinary mind is fallen mind: it falls against its objects, losing itself in their multiplicity and scattering itself in the process. The unity of mind is lost in the diaspora of sense objects. To recuperate from this self alienation one needs to re-collect and re-member. Anamnesis! The need for remembrance, however, cannot be self-generated: the call to at-one-ment has to come from beyond the horizon of centrifugal mind. One has to have already some sense of the Unseen Order, a natural and innate sense, not an intellectual opinion, a sense of "the existence of a reality superior to that of the senses." (Julius Evola, The Doctrine of Awakening: The Attainment of Self-Mastery According to the Earliest Buddhist Texts, p. 43.)
My conclusion is that no one is likely to take up, and stick with, serious meditation, meditation as part of a spiritual quest, unless he is the recipient of a certain grace, a certain free granting ab extra. (Here I go beyond Pali Buddhism which leaves no place for grace.) He must be granted a glimpse of the inner depth of the self. But not only this. He must also be granted a willingness to honor and not dismiss this fleeting intimation, but instead center his life around the quest for that which it reveals.
I would say that this also holds for the Buddhist whose official doctrine disallows grace and 'other-power.' Supposedly, the Tathagata's last injunction as he lay dying was that we should be lamps unto ourselves. Unfortunately, we are not the source of our own light.
I conjecture that what Buddha was driving toward in a negative way with his denials of self, permanence, and the possibility of the ultimate satisfaction of desire (anatta, anicca, dukkha) is the same as what Augustine was driving at in a positive way with his affirmations of God and the soul. Doctrinally, there is of course deep difference: doctrines display on the discursive plane where difference and diremption rule. But doctrines are "necessary makeshifts" (F. H. Bradley) that point toward the transdiscursive. Buddhists are famously open to the provisional and makeshift nature of doctrines, likening them to rafts useful for crossing the river of Samsara but useless on the far side. Christians not so much. But even Christians grant that the Word in its ineffable unity is not a verbal formulation. The unity of a sentence without which it would be a mere list of words points us back to the ineffable unity of the Word which, I am suggesting, is somehow mystically one with what the Buddha was striving for.
The depth of Buddha is toto caelo different from the superficiality of Hume and Sartre. For one thing, there was no soteriological/therapeutic intent behind Hume's reduction of the self to a mere bundle of perceptions. Secondly, it is arguable that the denial of a substantial self on the samsaric plane presupposes the Atma of the Upanishads, as Evola convincingly argues. More on this later.