While researching an answer to another question, I inadvertently discovered the answer to this question.
It appears that this most likely would have been understood in the context of stoicism; most likely in the context of secular Hellenistic Jewish philosopher Philo Judaeus of Alexandrea, a follower of stoicism.
In response to Plato's explorations of whether abstract qualities (Such as justice and wisdom) have an independent existence (and his argument that these things do not truly "exist" by appealing to his Theory of Forms), Stoicism taught that these things did exist materially and in a corporeal form or "substance" (οὐσία).
According to the Stoics, the universe is a material, reasoning substance, known as God or Nature, which the Stoics divided into two classes, the active and the passive. The passive substance is matter, which "lies sluggish, a substance ready for any use, but sure to remain unemployed if no one sets it in motion." The active substance, which can be called Fate, or Universal Reason (Logos), is an intelligent aether or primordial fire, which acts on the passive matter:
The universe itself is God and the universal outpouring of its soul; it is this same world's guiding principle, operating in mind and reason, together with the common nature of things and the totality that embraces all existence; then the foreordained might and necessity of the future; then fire and the principle of aether; then those elements whose natural state is one of flux and transition, such as water, earth, and air; then the sun, the moon, the stars; and the universal existence in which all things are contained.
— Chrysippus, in Cicero, De Natura Deorum, i. 39
Stoicism also taught that
everything that exists depends on two first principles which can be neither created nor destroyed: matter, which is passive and inert, and the logos, or divine reason, which is active and organizing. The 3rd-century B.C. Stoic Chrysippus regarded pneuma as the vehicle of logos in structuring matter, both in animals and in the physical world. Pneuma in its purest form can thus be difficult to distinguish from logos or the "constructive fire" (pur technikon)
Perhaps by studying stoicism and noticing the Septuagint's use of pneuma (πνεῦμα) in Genesis 1:1,
ἡ δὲ γῆ ἦν ἀόρατος καὶ ἀκατασκεύαστος καὶ σκότος ἐπάνω τῆς ἀβύσσου καὶ πνεῦμα θεοῦ ἐπεφέρετο ἐπάνω τοῦ ὕδατος
this led Philo to conclude that the πνεῦμα θεοῦ (pneuma theou - Spirit of God) was the Logos (The Reason, thought or word for the formation of the universe.)
In his writings, Philo
...used the term Logos to mean an intermediary divine being, or demiurge. Philo followed the Platonic distinction between imperfect matter and perfect Form, and therefore intermediary beings were necessary to bridge the enormous gap between God and the material world. The Logos was the highest of these intermediary beings, and was called by Philo "the first-born of God". Philo also wrote that "the Logos of the living God is the bond of everything, holding all things together and binding all the parts, and prevents them from being dissolved and separated".
Plato's Theory of Forms was located within the Logos, but the Logos also acted on behalf of God in the physical world. In particular, the Angel of the Lord in the Hebrew Bible (Old Testament) was identified with the Logos by Philo, who also said that the Logos was God's instrument in the creation of the universe.
It seems that Philo was attempting to synthesize Jewish thought and Hellinistic Philosophy. Thus, Philo wrote that,
In the first place therefore, from the model of the world, perceptible only by intellect, the Creator made an incorporeal heaven, and an invisible earth, and the form of air and of empty space: the former of which he called darkness, because the air is black by nature; and the other he called the abyss, for empty space is very deep and yawning with immense width. Then he created the incorporeal substance of water and of air, and above all he spread light, being the seventh thing made; and this again was incorporeal, and a model of the sun, perceptible only to intellect, and of all the lightgiving stars, which are destined to stand together in heaven.
And air and light he considered worthy of the pre-eminence. For the one he called the breath of God, because it is air, which is the most life-giving of things, and of life the causer is God
It seems then, that John 1, in claiming that
In the beginning was the Logos and the Logos was with God"
John was, to some degree, affirming the teachings of Philo (either directly or indirectly) and attempting to Join the Stoics philosophical dialogue. John goes on to affirm aspects of Philo's Cosmogony, saying
He was with God in the beginning. Through him all things were made; without him nothing was made that has been made. In him was life, and that life was the light of all mankind. The light shines in the darkness, and the darkness has not overcome it.
But then John takes it a step further and refines Philo's teachings in a corrective, saying not just that the Logos was with God at the beginning but that "The Logos WAS God" and that
He was in the world, and though the world was made through him, the world did not recognize him. He came to that which was his own, but his own did not receive him.
The Logos became flesh and made his dwelling among us. We have seen his glory, the glory of the one and only Son, who came from the Father, full of grace and truth.
And of course, according to John that was Jesus and the embodiment of these abstract qualities did exist corporeally - in Jesus. John is also claiming that Jesus is the "light" or pneuma, offering a corrective to Philo's belief that God
created the incorporeal substance of water and of air, and above all he spread light, being the seventh thing made
Instead claimng that the Logos is both God and the Pneuma (holy spirit) - which has implications for triniterianism that many miss in the text.
As it turns out, Philo's ideas are directly responsible for parts of the Nicene creed. According to the Internet Encyclopedia of Philosophy,
The other category apprehends him through himself, as light is seen by light. For God gave man such a perception "as should prove to him that God exists, and not to show him what God is." Philo believes that even the existence of God "cannot possibly be contemplated by any other being; because, in fact, it is not possible for God to be comprehended by any being but himself " (Praem. 39-40). Philo adds, "Only men who have raised themselves upward from below, so as, through the contemplation of his works, to form a conjectural conception of the Creator by a probable train of reasoning" (Praem. 43) are holy, and are his servants. Next Philo explains how such men have an impression of God's existence as revealed by God himself, by the similitude of the sun (Mut. 4-6) a concept which he borrowed from Plato. As light is seen in consequence of its own presence so, "In the same manner God, being his own light, is perceived by himself alone, nothing and no other being co-operating with or assisting him, a being at all able to contribute to pure comprehension of his existence; But these men have arrived at the real truth, who form their ideas of God from God, of light from light" (Praem. 45-46). As Plato and Philo had done, Plotinus later used this image of the sun. Thus the Logos, eternally created (begotten), is an expression of the immanent powers of God, and at the same time, it emanates into everything in the world.
This then means that the section of the Nicene creed reading
Light of Light, very God of very God, begotten, not made, being of one substance with the Father;
are a direct result of these ideas and philosophical arguments attributed to Philo and Plato.