To be objective is to adhere strictly to truth-conducive methods in one's thinking, particularly, to take into account all available information, and to avoid any form of prejudice, bias, or wishful thinking. The forms of observation and experimentation, and the canons of deductive reasoning and inductive reasoning employed by scientists practicing the verification guide scientists to be objective.
As stated earlier, the term "objective" can be applied to methods used in this process or results produced by it. For example, if a study to determine the effectiveness of a pharmaceutical drug is double-blind, randomized, and placebo controlled, the study can be called "objective" because it adheres to methods that are known to improve the reliability of its results.
Law, medicine, and almost every academic field have developed rules of evidence and guidelines for objectivity particular to their subject matter. In history, for example, objectivity is achieved through the use of the historical method and peer review of journal articles in which authors' proposed explanations and analyses of historical events are evaluated by other experts, prior to publication.
It is a matter of dispute among experts to what degree aesthetic and ethical judgements, as well as judgements involving the interpretation of the law, can be objective. Some hold that the beauty or merit of artworks and literary works cannot be objectively decided. Others deny this. Some claim that ethical judgements are relative to an individual's values or to the norms, mores, and folk-ways of society. Others deny this. There are impressive arguments on both sides.
In philosophy, an objective fact means a truth that remains true everywhere, independently of human thought or feelings. For instance, it is true always and everywhere that '2 plus 2 equals 4'. A subjective fact is a truth that is only true in certain times, places or people. For instance, 'That painting is beautiful' may be true for someone who likes it, but not for everyone.
The above examples are non-controversial. There are, however, other issues considered objective by some, not all. The role of Evolution vs. Intelligent design in the formation of living organisms is a typical example. Here, there are more objective arguments to support evolution than creation. Hence, an objective person will conclude that evolution is the most objective explanation. This illustrates that the objectivity of a theory does not depend on the approval of all. Sometimes, the objective opinion is held by a minority as, for example, Copernicus and Galileo's theories on the rotation of the Earth.
The scientific virtue known as simplicity or parsimony has also come to be known as "Ockham’s Razor" because of its frequent use by the fourteenth century philosopher William of Ockham, whose primary statement of the principle in his nominalist epistemology is that in accounting for the facts nothing should be assumed as necessary unless it is established through evidentiary experience or reasoning, or is required by the articles of faith.
Objectivism, or metaphysical objectivism, is the view that there is a reality or realm of objects and facts existing wholly independent of the mind. Stronger versions of this claim might hold that there is only one correct description of this reality; they may or may not hold that we have any knowledge of it. If it is true that reality is independent of the mind, the reality of objectivism is thus inclusive of objects which one may not know about and are not the intended objects of mental acts. Objectivity in referring requires a definition of what is true, and is distinct from the objects themselves which cannot be said to be true or false. An object may truthfully be said to have this or that attribute, such as the statement "This object exists", whereas the statement "This object is true" or "false" is meaningless. Thus, only references, or the statements one makes about objects without assigning truth value to the object itself, are true or false. Essentially, the terms "objectivity" and "objectivism" are not synonymous, with objectivism being an ontological theory to which a method of objectivity would apply.
Plato's realism was a form of metaphysical objectivism, holding that the Ideas exist objectively and independently. Berkeley's empiricist idealism, on the other hand, could be called a subjectivism: he held that things only exist to the extent that they are perceived. Both theories claim methods of objectivity. Plato's definition of objectivity can be found in his epistemology, which takes as a model mathematics, and his metaphysics, where knowledge of the ontological status of objects and ideas is resistant to change. Plato considered knowledge of geometry as a condition of philosophical knowledge, both being concerned with universal truths. Plato's opposition between objective knowledge and doxa (opinions) would become the basis for later philosophies intent on resolving the problem of reality, knowledge and human existence. Personal opinions belong to the changing sphere of the sensible, opposed to a fixed and eternal incorporeal realm which is mutually intelligible. Where Plato distinguishes between what and how we know things (epistemology) and their ontological status as things (metaphysics), subjectivism such as Berkeley's and a mind dependence of knowledge and reality fails to make the distinction between what one knows and what is to be known, or in the least explains the distinction superficially. In Platonic terms, a criticism of subjectivism is that it is difficult to distinguish between knowledge, doxa, and subjective knowledge (true belief), distinctions which Plato makes.
The importance of perception in evaluating and understanding objective reality is debated. Realism sides that perception is key in directly observing objective reality, while instrumentalism holds that perception is not necessarily useful in directly observing objective reality, but is useful in interpreting and predicting reality. The concepts that encompasses these ideas are important in the philosophy of science.
The term, "ethical subjectivism," covers two distinct theories in ethics. According to cognitive versions of ethical subjectivism, the truth of moral statements depends upon people's values, attitudes, feelings, or beliefs. Some forms of cognitivist ethical subjectivism can be counted as forms of realism, others are forms of anti-realism. David Hume is a foundational figure for cognitive ethical subjectivism. On a standard interpretation of his theory, a trait of character counts as a moral virtue when it evokes a sentiment of approbation in a sympathetic, informed, and rational human observer. Similarly, Roderick Firth's ideal observer theory held that right acts are those that an impartial, rational observer would approve of. William James, another ethical subjectivist, held that an end is good (to or for a person) just in case it is desired by that person. According to non-cognitive versions of ethical subjectivism, such as emotivism, prescriptivism, and expressivism, ethical statements cannot be true or false, at all: rather, they are expressions of personal feelings or commands. For example, on A. J. Ayer's emotivism, the statement, "Murder is wrong" is equivalent in meaning to the emotive ejaculation, "Murder, Boo!"
According to the ethical objectivist, the truth or falsity of typical moral judgments does not depend upon the beliefs or feelings of any person or group of persons. This view holds that moral propositions are analogous to propositions about chemistry, biology, or history: they describe (or fail to describe) a mind-independent reality. When they describe it accurately, they are true --- no matter what anyone believes, hopes, wishes, or feels. When they fail to describe this mind-independent moral reality, they are false --- no matter what anyone believes, hopes, wishes, or feels. There are many versions of ethical objectivism, including various religious views of morality, Platonistic intuitionism, Kantianism, and certain forms of contractualism and ethical egoism. Note that Platonists define ethical objectivism in an even more narrow way, so that it requires the existence of intrinsic value. Consequently, they reject the idea that contractualists or egoists could be ethical objectivists.