Seneca was a Roman stoic philosopher and an important statesman during the reign of Nero. His letters give us some insight into the ideas circulating in Rome around the time of the apostles. Here, for example, is what Seneca has to say about religious observation and the quest for wisdom.
You are doing the finest possible thing and acting in your best interests if, as you say in your letter, you are persevering in your efforts to acquire a sound understanding. This is something it is foolish to pray for when you can win it from your own self. There is no need to raise our hands to heaven; there is no need to implore the temple warden to allow us close to the ear of some graven image, as though this increased the chances of our being heard. (Letter XLI)
At first it appears that Seneca is advocating pure humanism. “The truth is within you… etc.” But when we read further, it becomes less clear cut than that. Seneca argues for the futility of religion but nevertheless maintains that a man cannot be good without God.
God is near you, is with you, is inside you. Yes, Lucilius, there resides within us a divine spirit, which guards us and watches us in the evil and the good we do. As we treat him, so will he treat us. No man, indeed, is good without God – is any one capable of rising above fortune unless he has help from God? He it is that prompts us to noble and exalted endeavors. In each and every good man, “A god (what god we are uncertain) dwells.” (quotation from Virgil, Aeneid, VIII)
If you have ever come on a dense wood of ancient trees that have risen to an exceptional height, shutting out all sight of the sky with one thick screen of branches upon another, the loftiness of the forest, the seclusion of the spot, your sense of wonderment at finding so deep and unbroken a gloom out of doors, will persuade you of the presence of a deity. (Letter XLI)
Is Seneca thinking of the deity as the Creator here? I am not sure. But what is certain is that Seneca sees evidence for the existence of a deity in the natural world. (Rom 1:19) Seneca also thinks of this deity as imminent. “God is near you, is with you, is inside of you.” The apostle Paul also emphasizes the nearness of God (Acts 17:27, cf. Rom 10: 7-8) but the dwelling of God’s Spirit is conditioned upon being made right with God through the Lord Jesus. I am not sure if Seneca conceives of God in this same personal way. That being said, Seneca does believe that God will judge us for the evil and the good that we do. Some of Seneca’s statements bear some resemblance to those of the apostle Paul. Some of the early church fathers maintained that Seneca corresponded with Paul which seems possible.