According to Osho, a true master cannot be proven by arguments; he is known by your immediate, existential response. Recognition flowers as spontaneous love, surrender, joy, a readiness to dance or laugh, humility and prayerfulness. A master asks not for explanations but for your transformation—show, don't say; your being, not your words, is the evidence.
You know a real master because being with them naturally makes you loving, joyful, humble, and moved to express it, not just talk about it.