Adjective
Of or relating to C. S. Lewis (1898–1963), writer and theologian, known for the children's fantasy series The Chronicles of Narnia and for non-fictional Christian apologetics.
Of or relating to Clarence Irving Lewis (1883–1964), American academic philosopher and the founder of conceptual pragmatism.
Of or relating to David Lewis (1941–2001), American philosopher.
Source: en.wiktionary.orgBirlinn. p. 93 state of the Lewisian gneiss bedrock of much of the Outer Hebrides that "these rocks are amongst the oldest to be found anywhere on the planet". Source: Internet
Smaller formations of Lewisian gneiss in the northwest are up to 3 billion years old. Source: Internet