•Why it earns a slot
Why it earns a slot: the Five Ways in Question 2 became the single most reused argument structure in Western philosophy, and this part alone runs 577 articles working out its consequences, from angelic movement to why food turns into flesh.
Aquinas sets out to prove God exists in five different ways, then spends 577 more articles working out everything that follows, from what angels are made of to why food becomes flesh.
This distillation is written from the freely available original, which is always the better read when you have the time: Project Gutenberg.