Talk of secularism is meaningful when it refers to the weakness of traditional religious belief or the lack of power of churches and other religious bodies. That is what is meant when we say Britain is a more secular country than the United States, and in this sense secularism is an achievable condition. But if it means a type of society in which religion is absent, secularism is a kind of contradiction, for it is defined by what it excludes. Post-Christian secular societies are formed by the beliefs they reject, whereas a society that had truly left Christianity behind would lack the concepts that shaped secular thought.