What is the prevailing philosophical background in the first century?

During the 1st century there is an environment in the pagan world that facilitated the birth and spread of Christianity. What were the origins? 1.Critique of polytheism. 2. Platonism: Platonic philosophy speaks of the future destiny of the immortal soul. There is an awareness that there is a life beyond in which we will have to give an account for what is done in this world. 3. Stoic philosophy: it offers rules of life by which society is governed. 4. Philosophy acts like a religion in the Roman world. Christianity is presented as a new monotheistic philosophy in which immortality is assured and its norms help the empire to function properly. All these causes contributed to the birth and expansion of Christianity.