You can download the audio book “Summa Theologica” by Saint Thomas Aquinas (1225-1274 AD) from LibriVox — via this link for Pars Prima, Initial Questions and via this link for Prima Pars, Trinity and Creation.
The Summa Theologica (or the Summa Theologiae or simply the Summa, written between 1265 and 1274) is the most famous work of Thomas Aquinas (c. 1225–1274) although it was never finished. It was intended as a manual for beginners as a compilation of all of the main theological teachings of that time. It summarizes the reasonings for almost all points of Christian theology in the West, which, before the Protestant Reformation, subsisted solely in the Roman Catholic Church.
The Summa’s topics follow a cycle: the existence of God, God’s creation, Man, Man’s purpose, Christ, the Sacraments, and back to God. (Summary adapted from the Wikipedia)
01 – Prologue; Question 1: The Nature and Extent of Sacred Doctrine – 00:45:47 02 – Question 2: The Existence of God – 00:21:22 03 – Question 3: On the Simplicity of God – 00:37:51 04 – Question 4: The Perfection of God – 00:15:06 05 – Question 5: Of Goodness in General – 00:29:37 06 – Question 6: The Goodness of God – 00:15:30 07 – Question 7: The Infinity of God – 00:20:54 08 – Question 8: The Existence of God in Things – 00:22:37 09 – Question 9: The Immutability of God – 00:11:57 10 – Question 10: The Eternity of God – 00:17:44 11 – Question 11: The Unity of God – 00:18:42 12 – Question 12: How God is Known by Us – 01:02:10 13 – Question 13: The Names of God – 00:35:49 14a – Question 14: The Knowledge of God – 00:40:34 14b – Question 14: The Knowledge of God – 00:42:08 15 – Question 15: Of Ideas – 00:16:19 16 – Question 16: Of Truth – 00:36:38 17 – Question 17: Of Falsity – 00:20:11 18 – Question 18: The Life of God – 00:23:39 19 – Question 19: The Will of God – 01:00:51 20 – Question 20: God’s Love – 00:23:48 21 – Question 21: The Justice and Mercy of God – 00:18:29 22 – Question 22: The Providence of God – 00:23:56 23 – Question 23: Of Predestination – 00:45:23 24 – Question 24: The Book of Life – 00:12:08 25 – Question 25: The Power of God – 00:34:49 26 – Question 26: The Beatitude of God – 00:10:38 27 – Question 27: The Procession of the Divine Persons – 00:28:58 28 – Question 28: The Divine Relations – 00:27:04 29 – Question 29 – The Divine Persons – 00:34:24 30 – Question 30: The Plurality of Persons in God – 00:26:17 31 – Question 31: Of What Belongs to the Unity or Plurality of God – 00:24:16 32 – Question 32: The Knowledge of the Divine Persons – 00:29:36 33 – Question 33: Of the Person of the Father – 00:23:06 34 – Question 34: Of the Person of the Son – 00:22:52 35 – Question 35: Of the Image – 00:08:02 36 – Question 36: Of the Person of the Holy Ghost – 00:34:51 37 – Question 37: Of the Name of the Holy Ghost–Love – 00:16:10 38 – Question 38: Of the Name of the Holy Ghost, as Gift – 00:09:00 39 – Question 39: Of the Persons in Relation to the Essence – 00:54:00 40 – Question 40: Of the Persons as Compared to the Relations or Properties – 00:25:54 41 – Question 41: Of the Persons in Relation to the Notional Acts – 00:36:55 42 – Question 42: Of Equality and Likeness among the Divine Persons – 00:37:15 43 – Question 43: The Mission of the Divine Persons – 00:41:28 44 – Question 44: The Procession of Creatures from God, and of the First Cause of all Things – 00:20:59 45 – Question 45: The Mode of Emanation of Things from the First Principle – 00:43:31 46 – Question 46: Of the Beginning of the Duration of Creature – 00:30:58 47 – Question 47: Of the Distinction of Things in General – 00:18:10 48 – Question 48: The Distinction of Things in Particular – 00:29:32
49 – Question 49: The Cause of Evil – 00:18:33