Irenaeus made a significant contribution to epistemology, psychology, and asceticism in late antiquity by establishing the first fully developed Christian framework for ascetic training that has come down to us. Irenaeus innovated in epistemology and psychology to direct the daily, embodied ascetic practices that enabled human beings to make progress towards union with God. Irenaeus developed an empirical epistemology from his physics of creation ex nihilo that focused ascetic training on structuring embodied perceptions in order to develop the ability to accurately discern the truth and to reliably choose the good. He produced a holistic psychology from his physics of embodiment that focused on training the soul to grasp the truth, have virtuous emotions, choose righteous actions, and follow the desires of the Spirit. Irenaeus taught that practising the ascetic disciplines of vigilant attention, meletē, and egkrateia every day was essential for structuring perception to grasp the essence of phenomena ‘as they are’, unveiling the true value of faith, righteousness, and union with God as the highest human good, and living an embodied life capable of enjoying the good without end.