Silence

[The Buddha said,]

Unanswerable propositions are not what I teach. What I teach, Mahamati, is getting free of what grasps and what is grasped and not giving rise to projections. Why should I be silent?

However, Mahamati, when someone is attached to what grasped or what is grasped and does not understand that these are nothing but perceptions of their own minds, then I am silent. Mahamati, the tathagatas [the Buddhas], the arhats, the fully enlightened ones use four kinds of explanations to teach others. Mahamati, I invariably use silence with those whose roots are not yet mature, not with those whose roots are mature.

---The Lankavatara Sutra---