Chapter 16: Internal Primes and Divisibility

Before we can define the ABCD coordinate chart, we need the concept of prime on τ-Idx. In standard mathematics, primes are imported from number theory as a background concept. In τ, primes are earned: they emerge from the divisibility relation on the internal natural numbers τ-Idx = O_α, using only the multiplication earned in the relevant chapter. This chapter defines divisibility, identifies the internal primes, and proves the Fundamental Theorem of Arithmetic on τ-Idx: every element n ≥ 2 has a unique factorization into primes.