According to Trinitarians, in John 1 is Jesus both the Word and the Light, and if so how do we make sense of John 1's wording?

Bible translators (especially the more literal translations) typically chose one word (English "in" in John 1:4) to translate one word in the source text (Greek "ἐν" in John 1:4). (I believe these two may even share a common Indo-Germanic root.) A slight problem with this approach is that the translated word may superficially mean the same as the source word, but does not necessarily carry with it all the implied usages from the source language, because in the target language the same implications do not always exist.

Anyone learning a foreign language will most probably have encountered the same problem: while speaking to a native speaker, their sentences may be grammatically flawless and even their pronunciation may be good, but the native speaker will soon catch on that they are a foreigner because they may use overly formal language, devoid of idiomatic usage and/or not understanding idiomatic language.

In English I don't think the idiomatic pattern is EVER used to say "something abstract is in a person". But it is used a couple of times in the New Testament. So what does it mean?

The Strong's Greek Dictionary has the following to say under entry G1722 ἐν:

a primary preposition denoting (fixed) position (in place, time or state), and (by implication) instrumentality (medially or constructively) ...

(Emphasis mine.) I think this already gives the biggest part of the answer to your concern: The phrase "In Him was life" simple means that He is instrumental in mediating or constructing "life".

I put life above in quotes because now one also has to be clear what is meant with life: mere biological life that is inside every living person by definition, or rather spiritual (everlasting) life? I would argue for the latter from the context of the gospels. Also, what is meant by light: the physical phenomenon involving photons and optics etc., or rather the moral principle that is by metaphor compared to the physical phenomenon? Again, I argue for the latter, because if it is the former, it would be as simple as lighting a candle/switching on the room's light to have Him around as a sort of captive audience. Obviously, in English, saying "I made him see the light" or "a wondrous light dawns upon me" talks about a change of insights, nothing to do with photons.

To sum up: don't read Scripture overly literally. Greek (And Hebrew) comes out of a long cultural tradition where poetry, metaphor and rhetoric (amongst others) were valued, so one is bound to find a lot of such language use in Scripture. When you take texts at literal face value and then get to paradoxes like you did or hair-splitting arguments, this may be one indication that you may not understand completely what the writer tries to convey. Rather try to get the gist of what the text is trying to say - maybe something like (my attempt at paraphrasing John 1:4): "He is the source and bringer of everlasting life, and in doing so He morally enlightened mortal humans so that they would see the error of their ways that would lead them to spiritual perdition, and also be able to find their way to everlasting spiritual life."

Notes

1. I understand that Strong's Dictionaries are considered quite inadequate for serious university-level theological study, so I do not try to espouse it as the one and only authoritative reference work. It is written to be accessible to lay people and generally gives a very good idea of the the meaning of words, though. Its copyright has also expired, so it is included in a plethora of Bible study software and websites, so it is extremely accessible to many people. If you have access to other reference works, surely do cross reference.

2. Some other instances (not an exhaustive list) in the New Testament that may be useful to contemplate: Luke 23:22, John 4:14 (literal water vs metaphorical water), John 6:56 (a strictly mathematical view holds that sets that mutually INclude each other are equal; which I don't think applies to Christ and a participant in Communion), John 7:18, John 8:44, John 9:3, John 11:10, Acts 17:28, 2 Cor 1:20, 2 Cor 5:21, Eph 1:4,7, Col 1:19, Col 2:9-10, 1 John 2:4-15, 1 John 3:5,9.

3. I also understand that this answer sidesteps any arguments for or against the divinity of Jesus the Messiah. This is on purpose. This may present (in most instances) another hair-splitting debate that draws the attention away from sound faith.

There are many statements in the Bible about God, the Son, and the Holy Spirit that appear to be paradoxes. Deliberately so, because the finite human mind has to be stretched to even begin grasping something of what God has chosen to reveal to us.

When asking if the Son of God is both the Word, and the Light, it is helpful to consider the connection between God and Light. It is not so helpful (in my view) to ask Trinitarians what their thoughts are on the Son being both the Word and the Light, because nobody needs to be a Trinitarian to believe what the Bible says about the Son in that regard. However, the question needs to be directed to a particular group to be acceptable to the site, so this answer is designed to bring in a trinitarian aspect by showing how God relates to both Word, and Light, just as the Son does.

John 1:1-3 is clearly linked in scripture to Genesis 1:1-10. When at creation there was Darkness, God spoke Light into being, by his Word. Now, God is Light, and in him is no darkness at all (1 John 1:5). Then we learn long after creation that the Son of God "is the true Light" that shines in the person of Jesus Christ. Genesis 1 shows that Light came to be there, at that particular time of creation, to deal with Darkness.

Interestingly, God said that the Light was good (Genesis 1:4) but nowhere does God ever say that Darkness is good. And God divides Light from the Darkness.

The paradoxes going on here are such that it's helpful not to limit our thinking to one human man being one thing, or another thing; to having qualities that are merely physical. We're dealing with that which is beyond time and space, existing before any material, universal creation. The Word was with God in the beginning, and was God, and made everything that was made.

Read the Genesis chapter 1 account with the advantage of now knowing how John chapter 1 speaks of the personification of the eternal, uncreated Word of God, the same Word of God that said "Let there be light" to divide darkness. Only True Light could do that! Only the true Word of God could do that. Both Light and Word are equally necessary and involved in the matter of physical creation, and in the nature of the one God. That is what John's opening statements about the Son of God are designed to get us thinking about.

Of course, those who consider the man Jesus to only have come into existence some 2,000 years ago, and who died around 33 years after he had been born, just won't be able to make any such connections as I have suggested. It would be impossible, so I'm not even going to try explaining. You may take or leave this answer, but it will be a waste of time probing with further comments. I shall not respond for I'm not here to justify my views, but I do hope paradoxical statements will not stop anyone from thinking in another direction - towards lux eterna and logos eterna.

In Trinitarian Christianity, one among the many reasons for God to "join humanity" by becoming one of us is to show us how to live according to God. Metaphorically, this can be compared to bringing a lamp into a dark room. John likens human's conscience as darkened by sin. When the room is dark, we don't see the dust and stains on the furniture. But once the window is opened and the sun's light shines on everything in the room, all those stains and dust become so visible and it becomes easier for us to clean.

Why do you have problem with this metaphorical language? God appears as human Jesus to be the "true light" as opposed to the "false light" that some Pharisees, Sadducees, scribes, and teachers of the law were. In this sense, John the Baptist brought light to the world too (v. 6-7), but John said that John the Baptist is a mere "witness about the light" (v. 8) to be surpassed by Jesus himself where his very being including His words, love, and actions served as "the light unto my path" that the Psalmist talks about (Ps. 119:105).

John 1:1-18 is one of my favorite passages. What always makes me almost crying is verse 10:

He was in the world, and the world was made through him, yet the world did not know him

Imagine you are God himself surveying in bodily form the world that you have created. You gave "life" to every human since all souls are created by God, and within each human life you provided "light" (conscience, v. 4). It is tragic that most in the "world" don't recognize you are God since their "light" have been darkened so the man who embodies "true light" is being charged as false prophet! (A true prophet is supposed to show the way, the "light".) But yet since Jesus is God, no demons can extinguish the source of all life and the light that shines from this source, hence verse 5:

The light shines in the darkness, and the darkness has not overcome it.

But those that accept Jesus, recognize the "true light". After they become Christians they are supposed to become light of the world themselves (!) following the example of Jesus, the "true light of the world" (John 1:9, 8:12). Jesus said in Matt 5:14-16:

¹⁴ “You are the light of the world. A city set on a hill cannot be hidden. ¹⁵ Nor do people light a lamp and put it under a basket, but on a stand, and it gives light to all in the house. ¹⁶ In the same way, let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven.

Why do you not make a fuss about us being "human" and "light" at the same time?

And God was the Word.

και θεος ην ο λογος

And in Him, Life was.

εν αυτω ζωη ην

And the Life was the Light ...

και η ζωη ην το φως ...

In God, is Life. And the Life (of God) is light.

God is (also) the Word.

I see no problem whatsoever.

(Unless, of course, one does not accept that the Son of God is 'very God of very God' as expressed by the Council of Nicea.)

All Greek quotations are from the Textus Receptus.

(Stephanus 1550, Beza 1598, Elzevir 1624 and Scrivener 1894 are all identical.)

The English is the literal English from the Greek text.

See the Englishman's Greek New Testament (interlinear, literal translation) 1870.