They did not abandon the Ancient Greek philosophical idea that everything is composed of four elements, and they tended to guard their work in secrecy, often making use of cyphers and cryptic symbolism.
ðeɪ dɪdnˌɑːt ɐbˈændən ðɪ ˈeɪntʃənt ɡɹˈiːk fˌɪləsˈɑːfɪkəl aɪdˈiə ðæt ˈɛvɹɪθˌɪŋ ɪz kəmpˈoʊzd ʌv fˈoːɹ ˈɛlɪmənts, ænd ðeɪ tˈɛndᵻd tə ɡˈɑːɹd ðɛɹ wˈɜːk ɪn sˈiːkɹᵻsi, ˈɔfən mˌeɪkɪŋ jˈuːs ʌv sˈaɪfɚz ænd kɹˈɪptɪk sˈɪmbəlˌɪzəm.