Irreligion (encompassing atheism, agnosticism, ignosticism, antireligion, skepticism, freethought, antitheism, apatheism, non-belief, secular humanism, or deism) varies in the different countries around the world.

Sixteen percent of the world population (1.1 billion people) are considered non-religious.

The Gallup poll has the most broad definition of irreligion: the question "Is religion an important part of your daily life?" was asked; the "no" answer is represented below. Dentsu Communication Institute provides data for respondents who stated they have "no religion". Phil Zuckerman uses the number who describe themselves as atheist or agnostic. The numbers come from different years, and might not be accurate for countries with governments that require or urge religion or secularism.

Countries with the greatest number of people without religion (including agnostics and atheists) based on the total population of each country as of 2004 compared to the percentage of nonreligious people according to Zuckerman:

This is a list of lists of countries and territories by various definitions, including FIFA countries, federations and fictional countries. A country or territory is a geographical area, either in the sense of nation (a cultural entity) and/or state (a political entity).

The characteristics of the human population:

The production, distribution and consumption of goods and services:

The value of goods and services produced within a country:

The physical, chemical, and biotic factors that act upon an ecosystem:

The Earth and its features:

The label for the country:

The process by which groups, often governments, make decisions:

Lists

Indices

Greg M. Epstein is the current secular humanist chaplain at Harvard University, and is a published author on the subject of secular humanism.

Epstein was born February 4, 1977 and grew up in the ethnically-diverse neighborhood of Flushing, Queens, New York. His parents, though Jewish, were not very religious, and he attended services with them only occasionally, usually during Jewish holidays or festivals. He describes this experience as one of the foundations for his later interest in Humanistic Judaism.

While attending the Stuyvesant High School in Manhattan, Epstein studied Buddhism and Taoism. After graduating from high school, he enrolled in the University of Michigan in Ann Arbor. As part of his undergraduate studies in the University of Michigan's College of Literature, Science, and the Arts, he spent a year in Taiwan in an effort to further his knowledge of Zen Buddhism through readings in Chinese and direct contact with Zen practitioners. Becoming disenchanted with Eastern religions during this experience, Epstein returned to the U.S. and completed his Bachelor of Arts in Religion and Chinese from the University of Michigan. He then went on to complete a Master of Arts in Judaic Studies, also from the University of Michigan.

Peter John Kreeft (born 1937) is a professor of philosophy at Boston College and The King's College. He is the author of numerous books as well as a popular writer of Christian philosophy, theology and apologetics. He also formulated, together with Ronald K. Tacelli, SJ, "Twenty Arguments for the Existence of God".

Kreeft took his A.B. at Calvin College (1959), and an M.A. at Fordham University (1961). In the same university he completed his doctoral studies in 1965. He briefly did post graduate studies at Yale University.

Kreeft has received several honors for achievements in philosophical reasoning. They include the following: Woodrow Wilson, Yale-Sterling Fellowship, Newman Alumni Scholarship, Danforth Asian Religions Fellowship, and Weathersfield Homeland Foundation Fellowship.

He joined the Philosophy faculty of the Department of Philosophy of Boston College in 1965. His intellectual reputation stems from his strengths in debating and summarizing the philosophical arguments of the major Western philosophers. He has debated several academics in issues related to God's existence. Shortly after he began teaching at Boston College he was challenged to a debate on the existence of God between himself and Paul Breines, an atheist history professor, which was attended by a majority of undergraduate students. Kreeft later used many of the arguments in this debate to create the Handbook of Christian Apologetics with then undergraduate student Ronald K. Tacelli, S.J..