With gandha and prithvi in place, Samkhya's twenty-five tattvas stand complete: purusha and prakriti as the two uncaused roots; mahat, ahamkara and manas as the antahkarana, the internal instrument; the ten sensory and active organs; the five tanmatras; and the five gross elements, akasha, vayu, tejas, apas and prithvi, each condensed from its matching tanmatra in a fixed and cumulative order. Every tattva after the first two is prakriti in a more differentiated form, and the whole chain, from unmanifest equilibrium to solid earth, is offered as a complete account of everything real apart from the many purushas that witness it.
What the chain explains, on Samkhya's own account, is not merely how many kinds of thing exist but why experience has the structure it does: why sound is the least demanding sense and smell the most, why earth seems denser and more richly textured than fire or air, why an organ of perception and an organ of action, though they may concern the same subject matter as with vak and shrotra, are never the same tattva. Each of these ordinary facts is derived rather than merely asserted, traced back through a specific sequence of evolutes to prakriti's original threefold guna constitution.
The twenty-five tattvas, taken as a set, are Samkhya's answer to the question of what is ultimately real, and the five tanmatras completed in this file are the hinge connecting the system's account of subjective experience, the eleven organs, to its account of the objective physical world, the five gross elements: the point at which what perceives and what is perceived are shown to share a single common origin.