Which Vijñāna Governs the Function of Thinking?

Thinking is divided into superficial thinking and deep thinking. Superficial thinking involves the vijnana (consciousness) thinking alone, which is superficial and cursory. Deep thinking involves the vijnana and manas (mind root) thinking together, which requires the power of concentration. With insufficient concentration, thinking remains at the surface level of the vijnana and cannot penetrate to the manas, thus failing to achieve true understanding or genuinely resolve problems. Consequently, the doubts in the mind remain unresolved.