You are probably a liberal if you reject the idea of the secular
In the introduction to his landmark study The Modernist Impulse in American Protestantism (1976), William R. Hutchison, the late professor of religious history at Harvard University, described the theological modernism (or liberalism) of a century ago in terms of three basic commitments. First, modernism sought to adapt religious ideas to modern culture. Second, modernism believed that God is immanent in and revealed through human cultural progress. Third, modernism was committed to a belief that society is progressively moving toward the realization of the kingdom of God.
All of this is standard fare for those familiar with Protestant liberalism, but Hutchison went on to note that the foundation of the modernist commitment to these three points was its rejection of the classic Christian distinction “between sacred and secular, between a starting point in revelation and a starting point in reason or in science” (8). As Hutchison put it, liberals “ordinarily refused to make automatic moral distinctions between church and world, or even between the religious and the secular” (9).
Hutchison argued that the experience of two world wars, the Great Depression, and the Cold War pretty much decimated liberalism’s confidence that the kingdom of God is being realized in the progress of society. But he pointed out that the most important emphasis of liberalism continued to endure in the theology of his day: “the attempt … to renounce long-standing categories of ‘religious’ and ‘secular’ probably constitutes the most important claim that modernism makes as a movement reaching beyond the needs and illusions of the time in which it flourished” (11).
Commenting on Hutchison’s book almost four decades later, I would note that this emphasis has won significant ground among Evangelical and even among confessional Reformed Christians. Even in the most conservative denominations Reformed theologians seeking to recover a healthy recognition of the difference between the kingdom of God and secular life (i.e., life in the present age) are subject to widespread criticism. Indeed, liberalism has been around for so long that many now regard its basic commitments as conservative Christianity, and speak freely about their fear that those trying to recover the old ideas are radicals at best, and liberals at worst. There is a lot of confusion out there. A lot of work needs to be done.