(The wave-particle duality, in which we can see how the same phenomenon can be perceived in two different ways, was one of the philosophical problems posed by quantum mechanics.)
The philosophy of physics refers to the set of philosophical reflections on the interpretation, epistemology and guiding principles of physical theories and the nature of reality. Although rarely the standard exposition of the physical theories discusses the philosophical aspects, the certain thing is that the philosophical conceptions of the scientists have had a leading role in the development of these theories. This was notorious from Newton and Kant, becoming very important in the twentieth century, when the theory of relativity led to a thorough analysis of issues traditionally studied in philosophy, such as the nature of time and space . The philosophy of physics contributes, through the criticism of the products of physics, feeding it back.
Interpretations of reality
In the human attempt to understand reality there have been three approaches to try to understand the development of physical events:
- The first is the mythical-religious approach, which seeks to know things based on the revelations, the tradition, and the content of the sacred books. In this interpretation, will or animation is attributed to the phenomena, in the same way that the behavior of other human beings seems to depend on unobservable thoughts. In this sense, both animist beliefs and theistic religions suppose that there are some kind of self-conscious minds (self-conscious natural forces, gods, spirits, etc.) whose voluntary actions are physical phenomena and therefore there is a possibility of human communication with said entities, which is the foundation of these religions.
- The second is the rationalist approach, by means of deductive reasoning; traditionally these are the preferred methods of both philosophy and mathematics, although in these have also used some observation and induction to guide the development of them.
- The third is the empirical approach, based on forming new knowledge through observation, experimentation and inductive reasoning. Physics is based mainly on this last way of looking for the truth, although it also makes a remarkable use of deductive reasoning.
The last two approaches assume that there are recurrent, timeless, and universal relationships in the way physical events occur, which are formulated in the form of logical propositions, called universal laws or physical laws (as opposed to mystical-religious interpretations, where there exist arbitrariness in the relation of some facts). Physics, and science in general, are attempts to discover the laws that govern the universe, based on known events, to understand the past and forecast the future behavior of nature. Philosophers of science are interested in questions such as the nature of scientific theories and their relation to the physical world, the way in which theories explain the phenomena of the world, the evidential and inferential basis of these theories and the way in which that evidence can be used to justify or discourage belief in a hypothesis.
The development of science is based on knowledge acquired through observation and experimentation, to predict, with the help of deductive reasoning, the future behavior of nature. The way in which scientists investigate and develop their theories is based on certain commonly assumed philosophical assumptions:
- Comprehensibility of the physical world, is to assume that nature is governed by laws that can be understood rationally by human beings. These laws are logical propositions whose truthfulness accounts for why certain patterns or relationships appear recurrently and constantly.Both the human being, like the rest of the animals, have evolved and acquired a broader intelligence, through time. However, the animals achieved a degree of intelligence which is sufficient only for the immediate purposes of their existence and their procreation. The discursive intelligence of human beings together with the complex cultural transmission from one generation to another, allowed them not only to satisfy the elementary biological functions, but also to construct abstract representations of the facts of the world.
The possibility of abstract conceptualization is exclusive, or almost exclusive, of human beings and higher primates. The cognitive abilities of human beings have allowed them to generalize about recurrent observed patterns, formulating laws that govern natural phenomena. It is fortunate that natural laws exist and that the intellectual capacity of the human being is sufficient to understand them (at least it seemed that way until the middle of the last century).
- Objectivity of the physical world, is to assume that physical phenomena are independent of the subject who observes them, or in other words there is intersubjectivity between different observers: two observers can agree on certain facts observed by both. There must also be temporal and spatial objectivity, that is, there are constant relationships and patterns that do not change from one place to another, or from one moment to the next.The consequences of an action here are the same as those that occur there, under the same action and in similar conditions. What happens today will be the same as what will happen tomorrow, if the conditions are similar.
- Consistency, there is only one truth about a particular event or phenomenon, regardless of the visions or interpretations that may be had about it. A very important aspect, on this postulate, is that there can not be two truths that are opposed and that are valid simultaneously. The philosophical assumption of consistency implies that propositions that are logically valid deductions of valid physical laws are facts that will be supported by experimental observations.
Problems of philosophy of physics
Among the issues dealt with by the philosophy of physics are:
- The purpose of physics refers to whether physics is a description of the real essence of phenomena and the nature of reality or only formally tracks and predicts quantitative and qualitative relationships between observable phenomena.
- Physical cosmology or the nature of space, time, the origin of the universe and its ultimate destination, as well as problems related to the existence and immanence of certain properties. Currently, physical fields and matter are conceived as excited states of space-time where energy is not close to the minimum possible, apparently space-time is a type of entity more basic than matter that would be possible configurations of the geometry of said space-time (something that reverses the classical conception of space and matter).
- The nature of thermodynamics and statistical mechanics, which deals with both the problem of determinism, and the role of information and how chance and probability should be interpreted in the context of physical theories. At the microscopic level, many equations of time evolution are reversible, that is, they are identical whether time travels forward or backward, however, macroscopically the universe seems to evolve irreversibly in the direction of maximum entropy.
- The quantum mechanics, on which there are discrepancies on what interpretation to give to the problem of the measure and to the fact that certain phenomena respond to probabilistic and non-deterministic descriptions.