Does Using the Manas to Recollect the Buddha and Think About Problems Feel Tiring?

When practicing recollection of the Buddha (buddhānusmṛti), just recite and that is enough; there is no need to rack your brain thinking about the Buddha's various merits and virtues, or about questions such as how to recite in order to achieve results. This consumes relatively little mental energy, effort, and vitality. If the time spent on recollection of the Buddha is not too long, and one eats normally, one will not feel particularly tired. However, when first learning to recite the Buddha with the manas, because one is not yet proficient, some mental effort is required, and one will feel somewhat tired. Once the recollection of the Buddha gradually enters a state of meditative absorption (samādhi), and the meditative concentration becomes relatively deep, the circulation of qi and blood is good, and the nourishment and energy are sufficient, there will be no feeling of tiredness; on the contrary, the physical body will feel tranquil and at ease (praśrabdhi), and the mind will be joyful. In a state of meditative absorption, very little energy is consumed.

Using the manas to think about problems is different from reciting the Buddha. Thinking about problems requires using the brain, and the consumption of mental energy, effort, and vitality is greater. If there is not an ample supply of energy, one will feel tired. When investigating Chan (canchan), it is mainly the manas that carries out the investigation and deliberation (manasikāra/manana), which requires mobilizing the nervous system. The energy consumption is high, so one will feel very tired. Therefore, those who investigate Chan will eat a bit more, people who use their brains a lot will eat more, and they need to take a rest after a period of time; otherwise, they will feel very tired. However, when meditative concentration is very deep, because the qi and blood are abundant, the energy supply can keep up, and one does not easily feel tired, whereas with shallow meditative concentration one easily feels tired. If the investigation of Chan enters a very deep state of meditative absorption, at that time the circulation of qi and blood is good, and body and mind are tranquil, at ease, and joyful, so one will not feel tired.

Deliberation with the manas consumes a great deal of energy, whereas thinking with the mind consciousness consumes less. Because deliberation with the manas requires engaging the brain and nervous system, it consumes energy, and so one feels tired. The nervous system of the entire body is mobilized by the manas and cannot be mobilized by the mind consciousness. Therefore, thinking with the mind consciousness is relatively easy; even if one is very scattered and distracted, thinking about everything, one will not feel very tired. For this reason, many people like to use the mind consciousness and are unwilling to engage in deep thinking and investigation.