Anti-realists believe that science is just a set of statements, it is a tool for humans to see the world, that’s why it cannot be objective and lead us to an ultimate goal as Popper told in his theory. By that logic, science depends on the individual, it is subjective; so it changes from person to person, no certainty for a single, neutral one. This is the reason why anti-realists treat science as invention instead of discovery.
Kuhn rejects progress in science and the method of falsification. To Kuhn, science is made up of a set of ideas, assumptions and worldviews taken as given and not subject to testing (paradigms), and scientific communities gathers around those paradigms, to form what he called Normal Science. In fact, the Paradigm as conceived by Kuhn is a sort of fundamentalist orthodoxy about how the world is. A whole generation of scientists grows up with a set of common assumptions and they exhibit strong resistance to any data that might call the central Paradigm into question. Kuhn states that scientists spend most (if not all) of their careers in a process of puzzle-solving. Their puzzle-solving is pursued with great tenacity, because the previous successes of the established paradigm tend to generate great confidence that the approach being taken guarantees that a solution to the puzzle exists, even though it may be very hard to find. Kuhn calls this process normal science. Normal Science is to Kuhn the process of elaboration of the Paradigm or central theory in ever more detail, so during the normal science periods, there is progress.
If an unexpected result occurs, this causes an anomaly. This can block the theory anymore, and uncertainty starts. As a paradigm is stretched to its limits, anomalies — failures of the current paradigm to take into account observed phenomena — accumulate. Their significance is judged by the practitioners of the discipline. Some anomalies may be dismissed as errors in observation, others as merely requiring small adjustments to the current paradigm that will be clarified in due course. Some anomalies resolve themselves spontaneously, having increased the available depth of insight along the way. But no matter how great or numerous the anomalies that persist, Kuhn observes, the practicing scientists will not lose faith in the established paradigm until a credible alternative is available; to lose faith in the solvability of the problems would in effect mean ceasing to be a scientist.
Once we reach a time of crisis (many unexplained analomis), it is a crisis, and radical changes occur. But in practice, Kuhn thought theories might only be replaced when the old guard dies out and a new generation replaces them who are not so invested in the old way of looking at things. The paradigm is sunk, and the system is replaced, a paradigm is changed by revolution. Scientific revolution is the phase in which the underlying assumptions of the field are reexamined and a new paradigm is established. In any community of scientists, Kuhn states, there are some individuals who are bolder than most. These scientists, judging that a crisis exists, embark on what Thomas Kuhn calls revolutionary science, exploring alternatives to long-held, obvious-seeming assumptions. Occasionally this generates a rival to the established framework of thought. The new candidate paradigm will appear to be accompanied by numerous anomalies, partly because it is still so new and incomplete. The majority of the scientific community will oppose any conceptual change, and, Kuhn emphasizes, so they should. To fulfill its potential, a scientific community needs to contain both individuals who are bold and individuals who are conservative. There are many examples in the history of science in which confidence in the established frame of thought was eventually vindicated. It is almost impossible to predict whether the anomalies in a candidate for a new paradigm will eventually be resolved. Those scientists who possess an exceptional ability to recognize a theory's potential will be the first whose preference is likely to shift in favour of the challenging paradigm. There typically follows a period in which there are adherents of both paradigms. In time, if the challenging paradigm is solidified and unified, it will replace the old paradigm, and a paradigm shift will have occurred. For Kuhn the scientific ideal is whatever has emerged as the dominant scientific community.
Two paradigms are incompatible and incommensurable which means two are not measurable by the same standards, values, langauage, terms and have no common basis for comparison according to Kuhn. As the people, especially the scientists would create different paradigms which are subjectively expressed and have its own language and worldview. The language of the theories that belong to Newton and Einstein are different from each other, they do not represent the same things. So these two theories are incompatible. Karl Popper will deny this quotation according his point of view and theories.
According to realism, science displays a process of discovery which means scientists deal with the things that already exist and one can discover those existing things that have not been realized before. Therefore, science is objective; as the scientists only discover the theories not inventing them. That’s why, the realists believe that the scientific improvements guide to a neutral, real truth common for everyone. The theory is used, and if it is falsified, then the new theory is build. If that latter theory is also falsified then a third one comes. The process continues like that as a chain which leads the scientific progress. So the realists and Karl Popper conclude that the scientific progress is a continuous process. In addition, this progress concludes a neutral language that means the same thing for everyone, same understanding for what is happening.
Kuhn sees the dominant paradigm as foundational, at least until it reaches a crisis. Popper on the other hand, insists we hack away at the very plank we are standing on to see if it holds up. Any scientific theory to Popper is always in the state of being not yet disproved.
