Subjectivism is the opposite of objectivism. Subjectivism is most clearly expressed by the philosophical theory that there is no independent truth outside of one’s own subjective experience, the subject being the human person and the human mind, with focus on the individual, and his or her interpretation of experience on which they base their beliefs and opinions, which may or may not correspond to reality. A subjective impression about anything or anyone is most often based on an informal interpretation, usually without complete knowledge or understanding of the facts of the matter, or the background of what is currently being perceived. It is contrasted with objectivism, the philosophical theory that truth exists objectively outside of personal experience and that, although we may not entirely understand objective truth, it exists as a reality external to the human person and the human mind, and it is absolute, the objective being physical and spiritual existence as distinctively real apart from and independent of one's self, and objectivity as the rational orientation of oneself to the conscious reality of facts and evidence that one has neither created nor can totally control, apart from one's subjective impressions or personal opinions or wishful thinking. Objective morality is predicated on the reality of objective standards of truth, in contrast to the moral vagueries of subjective relativism.
The fact that all human experience of external reality is only indirectly mediated by the physical senses as interpreted by the brain and the relative level of intelligence of the individual is cited by some as the reasonable source of skeptical doubt about knowledge of truth and reality. Historically, and ordinarily, conclusions based on one's own interpretation of reality are not always reliable. People make mistakes. Whatever available information is informally or formally gathered from personal experience and from other sources and found immediately at hand is often not complete, and often is interpreted wrongly, resulting in false conclusions and erroneous research colored by subjective impressions and assumptions which obscure objective perceptions of the available evidence. Innocent persons have been persecuted, convicted and destroyed by others solely on the basis of subjective judgment, socially, ethnically, and in courts of law.
Subjectivism fundamentally asserts that truth is wholly and entirely subjective and that it is finally only an illusion basically dependent on the subject’s mind and experience—we create our own reality. Subjectivism is similar to relativism in asserting absolutely that what is true for one person may not be true for another, and therefore that nothing is absolutely true (including the absolute assertion that nothing is absolutely true). Truth is reduced to personal opinion, often as the expression of a collective belief held in common by a large community of individuals who agree on what they confidently assert is true.
The philosophical subjectivism of atheists is rooted in the confirmation bias of a naturalism which prejudicially dismisses all possibility of entertaining as truth the objective reality of divine revelation in the Person of Jesus Christ.
Fallacy of analogy
Swinburne's argument from religious experience
Toward a Subjective Theology of Revelation, Thomas Franklin O'Meara, O.P., Thomas Aquinas Institute of Theology, Dubuque (cdn.theologicalstudies.net) "Roman Catholic theology (always with some exceptions) has tended to concentrate on the objectivity of revelation."
The Doctrine of Revelation: How God Reveals His Nature and His Will, Rick Wade (probe.org) "Revelation comes to us in two basic forms: general or natural revelation, and special revelation (includes His spoken word, His written word, and His Son).... It is knowledge that comes to us from outside ourselves and beyond our ability to discover."