Do the first five consciousnesses have the function of thinking?

The first five consciousnesses also have the five universal mental factors: attention (manaskāra), contact (sparśa), feeling (vedanā), perception (saṃjñā), and volition (cetanā), only theirs are simpler and coarser than the five universal mental factors of the sixth and seventh consciousnesses. The sixth and seventh consciousnesses deliberate on mental sense-objects, and their deliberation can be very fine and profound; the first five consciousnesses deliberate on the five sense-objects, and their deliberation is very coarse and simple. As long as you can separate the five sense-objects from the mental sense-objects and avoid confusing them, you can distinguish the volition of the five consciousnesses from that of the sixth and seventh consciousnesses. The volition of the five consciousnesses is not the kind of deliberative function that the mind consciousness has; the two are different, and the difference is quite substantial. Being able to separate the five sense-objects from the mental sense-objects is extremely difficult, so being able to distinguish the discernment of the five consciousnesses from that of the mind consciousness is also very hard. Likewise, most people cannot distinguish the functions of the manas from those of the mind consciousness.

What people ordinarily call deliberation generally refers to the sixth and seventh consciousnesses' deliberation on mental sense-objects, especially the solitary mental consciousness's deliberation on Image-Only Objects, and the five consciousnesses cannot but participate in it. The volition among the five universal mental factors of the five consciousnesses mainly serves the function of judgment and decision. After the five consciousnesses discern their corresponding five sense-objects, they take the marks of those objects, make a simple and coarse judgment, and then decide whether to continue discerning or to stop and avoid them, with the mind consciousness simultaneously participating in the discernment. The reason the discernment of the five consciousnesses is said to be coarse is that the five sense-objects are coarse and require no fine discrimination; therefore the discernment is swift and the five consciousnesses need not expend much mental effort, as if it did not go through the brain at all. The mental sense-objects that accompany the five sense-objects, however, are relatively subtle and require the fine discernment of the mind consciousness, so the mind consciousness's discernment and analytical thinking are both slower and more mentally taxing.

When the five sense-objects are significant and their impact is great, the manas takes the judgment and decision of the five consciousnesses as the primary basis for its own decision, with no time to process the mind consciousness's analysis and judgment, and so it disregards the mind consciousness's discernment and deliberation. Usually the discernment of the five consciousnesses is rather direct and swift, while the discernment of the mind consciousness is finer and slightly slower than that of the five consciousnesses. In major matters, the manas relies mainly on the reactions of the five consciousnesses and cannot attend to the reactions of the mind consciousness. Thus, in some sudden emergencies, there is no time for the mind consciousness's analysis and deliberation; the manas directs the matter to completion, leaving the mind consciousness to realize it only after the fact. To sum up: deliberation refers to the deliberation of the sixth and seventh consciousnesses; the volition of the first five consciousnesses is simpler, coarser, and more direct than deliberation—not deep enough, and it does not need to be deep, because the five sense-objects and their dharmas are shallow, coarse, and direct.