The Trinity is a unique and important Christian concept, but some people have expressed the opinion that this concept is illogical. It is interesting in this regard that the English word logical is derived from the Greek adjective λογικός, which is related to the word λόγος (usually translated as word) that is used in John’s Gospel to refer to the second person of the Trinity (see John 1:1, 14).
According to Liddell and Scott, the word λόγος denotes “the word by which the inward thought is expressed,” and additionally “the inward thought or reason itself” (Henry George Liddell and Robert Scott, A Lexicon: Abridged from Liddell and Scott’s Greek-English Lexicon [Oxford: Oxford University, 1983], 416). The adjective λογικός also reflects this basic dual semantic potential of the word λόγος. Thus, λογικός can mean “belonging to speech or speaking,” or “belonging to reason, rational” (ibid.).
From the point of view of the Greek language used in the prologue of John’s Gospel (i.e., John 1:1–18), we have to say that the concept of the Word is λογικός. The Logos expresses the rationality or thought of God the Father that the latter has chosen to express (John 1:18).
Extrapolating from John’s depiction of the second person of the Trinity as ὁ λόγος, we can say that the totality of the concept of the Trinity is itself distinctly logical. The logic involved is the logic of the Father expressing himself through the Son and the Spirit. Being the self-expression of the Father, the Son and the Spirit possess the same divinity as their eternal source, God the Father.
