There is no secular creed, so start by asking rather than assuming. Broadly: an atheist holds that there is no God, or no good reason to believe in one; an agnostic holds that the question cannot be settled, or that they personally have not settled it; and a great many people are simply secular, living without reference to God, not hostile, not curious, occupied with other things. Common threads, when they are articulated: that the sciences give us the most reliable knowledge we have, and that what cannot be tested should be held loosely; that the universe and life are explained by physics and evolution without a designer; that morality is real but human, grounded in our shared nature, our reasoning and our need to live together, not in divine command; that religions are human constructions, often sincere and sometimes beautiful, which have also done harm; that suffering and evil count against a good and powerful God; that the many religions cancel each other out; and that meaning is something we make rather than find. Many secular people were raised in a church and left it, and the leaving usually had a reason: an unanswered question, a hypocrisy they watched up close, a scientific claim the church seemed to deny, a hurt. Younger secular people are often less argued out of faith than never argued into it; the question simply did not come up. Most are decent, thoughtful, and tired of being treated as a project. Some hold their view with real intellectual seriousness and have read more philosophy of religion than most Christians; assume that until you learn otherwise.
Where to read it for yourself
- David Hume, Dialogues Concerning Natural Religion (1779): the classic statement of the problem of evil and of doubts about design
- Bertrand Russell, Why I Am Not a Christian (1927): the standard modern objections in short form
- Richard Dawkins, The God Delusion (2006): the popular case that science makes God unnecessary
- Christopher Hitchens, God Is Not Great (2007): the moral case against religion
- Sam Harris, The Moral Landscape (2010): the attempt to ground morality in wellbeing without God
- Pew Research Center, Religious Landscape Study: the growth of the religiously unaffiliated and what they actually believe, which is more varied than the label