ɡlˈɛn ˈɛldɚ θˈiəɹaɪzd ðə lˈaɪf kˈoːɹs æz bˈeɪst ˌɔn fˈaɪv kˈiː pɹˈɪnsɪpəlz: lˈaɪfspˈæn dɪvˈɛləpmənt, hjˈuːmən ˈeɪdʒənsi, hɪstˈɔːɹɪkəl tˈaɪm ænd dʒˌɪəɡɹˈæfɪk plˈeɪs, tˈaɪmɪŋ ʌv dᵻsˈɪʒənz, ænd lˈɪŋkt lˈaɪvz.
Glen Elder theorized the life course as based on five key principles: life-span development, human agency, historical time and geographic place, timing of decisions, and linked lives.