The surest way to alter human consciousness is

Psychoactive drugs are the surest, fastest way to alter consciousness because they directly affect neurochemistry - receptors, neurotransmitters (dopamine, serotonin). Meditation, sleep, and sensory deprivation can alter consciousness but are slower, less reliable, and don't guarantee change. Drugs produce immediate, predictable effects on conscious experience (pain relief, euphoria, hallucinations).