Karl Popper: Philosophy of science and logical reasoningJune 27, 2021
We often think that science proves truths about the world.
We imagine that a good scientific theory is one that definitively proves the truth. But Karl Popper insists that this is not the case. According to him, what makes a theory scientific is its capacity to be falsified or to be shown to be false through experience.
Popper is concerned with the way science finds out about the world. Science is based on experiment and experience. If we want to do science well We need to take a closer look at what David Hume calls the regularities of nature—the fact that events in the world take place in certain orders and sequences that can be studied systematically. In other words, science is empirical, or based on experience, and in order to understand how it works, we need to understand how experience often gives rise to knowledge. Consider the following statement: “If you throw a tennis ball out of a second-floor window, it will fall to the ground.” We can be absolutely sure of the plausibility of this proposition if we set aside chance events (like the ball being snatched away by a passing eagle). If someone comes out and says, “Wait a minute, are you sure the ball is going to hit the ground?” If he asks, we’ll think he’s weird. But how do we know when we throw the ball? What kind of information is this?
The short answer to this is: We know, because it has always been so. Incidentally aside, no one has ever seen a tennis ball climb up or hover when released. We know it will fall to the ground because experience has shown us that it will. Not only do we know when the ball will hit the ground, we also know how it will fall. For example, if we know the gravitational force and the height of the window from the ground, we can calculate how fast the ball will fall. Nothing about this event is the least bit mysterious.
But the question still stands: Can we be sure that the next time we throw the ball, it will hit the ground? No matter how many times we do the experiment and how sure we are of the result, we cannot prove that the result will be the same in the future.
The inability to speak with certainty about the future is called the problem of induction and was first introduced by David Hume in the 18th century. So what is inductive logic? Induction is the process of drawing a set of observed facts about the world to more general conclusions about the world. When we throw the ball, we expect it to hit the ground because, at least according to Hume, we have had countless similar experiences where objects like balls fall to the ground when we let them go, and we generalize them.
Another form of reasoning that philosophers compare to induction is deductive reasoning. Induction goes from a special case to the general whereas deduction comes from a general case to the particular. For example, a deductive chain of logic begins with two propositions: “If this is an apple, then it is a fruit.” (since all apples are fruit) and “This is an apple.” Given the nature of these propositions, the statement “This is an apple” would inevitably result in “This is a fruit”.
Philosophers like to simplify deductive arguments by writing them in signs. Then the above argument would be: “If p then it is q; it is q because p is.” In our example, “p” stands for “This is an apple,” while “q” stands for “This is a fruit.” If we have “If p then q” and “p” as the starting point then our result is q necessarily or inevitably true.
Another example would be: “If it’s raining, the cat will meow (since all cats meow when it rains). It’s raining, then: The cat will meow.” All such arguments are accepted by philosophers as valid arguments; because its consequences inevitably follow propositions. However, that an argument is valid does not mean that its conclusions are true. For example, “If it’s a cat then it’s banana flavored; It’s a cat, then it’s banana flavored” is valid because it follows a valid format. But most people will agree that your conclusion is wrong. And a closer look shows that there is an empirical problem with the proposition “If it’s a cat, then it’s banana-flavored” because cats, at least in our world, are not banana-flavored. In other words, because the proposition is not true, the conclusion is not true even if the argument is valid. Other worlds can be envisioned in which cats are indeed banana-flavored, and so the expression non-banana-flavored may be true on a logical or, if not necessarily true, basis—forcing it to be true in all possible worlds. However, arguments that are valid and have correct propositions are called “valid”. The banana-flavored cat argument is valid but not healthy, as we’ve seen. The argument about apples and fruit though is both valid and healthy.
Prepared by: Sociologist Ömer YILDIRIM
Source: Omer YILDIRIM’s Personal Lecture Notes. Atatürk University Sociology Department 1st Year “Introduction to Philosophy” and 2nd, 3rd, 4th Grade “History of Philosophy” Lecture Notes (Ömer YILDIRIM); Open Teaching