By science I mean what is generally meant by, natural science, which includes physics, astronomy, chemistry, biology, and medicine, and only includes those aspects of those sciences which are rigorously and definitely established without possible controversy. I identify these as true science.
Everything else that goes by the name science may use many of the same methods as true science, and in some cases are quite rigorous, but they all fail the tests for a true science at some point. I use the following criteria for the identification of a true science:
True science has two parts: method and content.
The method of science is the means used to establish scientific principles, sometimes called laws, which correctly identify aspects of the physical world, its entities, their properties, relationships, and behavior (events).
The content of science is the body of established scientific principles excluding all opinions, conjectures, unproven hypotheses, or anything established by the unscientific methods of statistics, surveys, concensus, or mere authority.
The overriding principle of science is objectivity. No discovery, no theory, no fact, and no method is science that is not based solely on reasoning from observed physical evidence.
The scientific method includes six characteristics: Observation, Hypothesis, Testing, Demonstrable, Repeatable, and Reliable (predictive).
Observation—All scientific enquiry begins with the observation of some physical phenomena, some entity, substance, or event that is not already identified or understood. The purpose of the scientific method is to discover an explanation for the observed phenomena.
Observation includes any methods of investigation necessary to fully examine or discover phenomena to ensure it is correctly identified and unique (that it is not something previously idenfied and explained).
[NOTE: The observation and identification aspect of science is sometimes mistaken for "induction." There is no such thing as inductive reasoning, only deductive reasoning.]
Hypothesis—Preliminary observation and investigation usually provides enough information to suggest a possible explanation of the nature of the phenomena. A plausible explanation considered as a possible explanation is called a hypothesis which can be anything from a, "wild guess," to a highly probable explanation.
A hypothesis must be provable. There must be some way to examine (test) a hypothesis that will demonstrate the explanation meets all the criteria for an established scientific principle. One test for any proposed hypothesis is called falsifiability, which only means, for a hypothesis to be a valid one, there must be a test that will prove it false, if it is false, else just any undisprovable thing could be suggested as a hypothsis from spirits to magic.
Testing Testing a hypothesis is any means, from examination to elaborate experimentation necessary to establish a hypothesis is correct. One certain test is one that will prove the hypothesis false if it is false. If that test fails to prove the hypothesis false, it proves it true. In any case a hypothesis is not fully proven until it meets the next three criteria: demonstrable, repeatable, and reliable.
Demonstrable The test of a hypothesis must be demonstrable. That is, it must be able to be demonstrated to any others capable of understanding the nature and purpose of the experiments or tests. Scientific proof cannot be esoteric. (Think global warming.)
Repeatable The test of a hypothesis must be repeatable. This does not mean a test must be repeated exhaustively (as implied by induction), only that anyone who performs the same experiment will get the same results.
Reliable (predictive) Any phenomena determined by an established scientific principle will always be the same when all pertinent context is the same. This is not to be mistaken for, "cause and effect," although it may be called "cause" so long as it is understood it only means, "the explanation for," a phenomenon.
The content of science is the body of established scientific facts and principles. There are tests for what can and cannot be included as established science. Only facts and principles established in conformance to the entire scientific method belong to established science. Only facts and principles that do not contradict any other established facts or principles belong to established science. Any contradiction means one or both of the supposed facts or principles is incorrect and until the contradiction can be resolved, neither fact or principle can be accepted as established science.
Other Things Called Science
Many things are called science today, including: geology, meteorology, ecology, psychology, sociology, cosmology, and evolution and literally hundreds more. If by science is only meant, "seeking for knowledge," (the root meaning of science) any legitimate intellectual discipline may be called science. If science is going to be used in this way, perhaps the physical sciences ought to be distinguished from everything else called science by calling natural science, "objective science," the study of the nature of that which exists and has the nature it has independently of anyone's awareness of it, opinions about it, or feelings about it; that is, the objective physical word we directly perceive.
All of the other things called science could then be called "cateloging sciences," like archaeology, paleontology, and taxonomy; "semi-objective sciences," which are a mixture of scientific methods and opinion, guesses, surmises, supposition, statistics, surveys, estimates, or other non-objective elements like geology, meteorology, ecology, psychology, sociology, climatology, oceanography, and anthropology; and "historical-origins sciences" which attempt to guess where everything came from like cosmology and evolution.
No view or position defended as being based on science, when the supposed science is anything other than an objective science is valid on that basis.