The Germ Hypothesis Part 1

Written by Mike Stone on May 22, 2024. Posted in Current News

According to the Encyclopaedia Britannica, the germ “theory” of disease, which states that certain diseases are caused by the invasion of the body by microorganisms too small to be seen, has “long been considered proved.”

Harvard University says that the “theory” was “developed, proved, and popularized in Europe and North America between about 1850 and 1920.” Wikipedia claims that the germ “theory” of disease is “the currently accepted scientific theory for many diseases.”

Papers published in scientific journals claim that Louis Pasteur and Robert Koch “firmly established the germ theory of disease” and that they “first proved the germ theory of disease in the second half of the nineteenth century.”

Thus, if we were to listen to what the mainstream sources declare, it would appear that the germ “theory” of disease has been scientifically proven based upon the evidence established by Louis Pasteur and Robert Koch. We are to believe that the work of these two men allowed for the initial germ hypothesis to be “proven” in order to be elevated to the status of a scientific theory.

However, is that truly the case? Did Pasteur and Koch provide the necessary scientific evidence required in order to confirm the germ hypothesis? What does it take to accept or reject a hypothesis? How does a hypothesis go on to become a scientific theory?

In the first of a two-part examination of the germ hypothesis looking at the work of both men, we will begin by inspecting two of Pasteur’s early attempts to prove his hypothesis in the cases of chicken cholera and rabies. We will investigate how he arrived at his germ hypothesis, and then look to see if his experimental evidence reflected anything that could be witnessed in nature.

In doing so, we will find out whether or not Louis Pasteur was ever able to validate and confirm his germ hypothesis.

What is a Hypothesis?

To begin this investigation, we need to understand what exactly a hypothesis is supposed to be. Returning to the Brittanica for a moment, a scientific hypothesis is defined as “an idea that proposes a tentative explanation about a phenomenon or a narrow set of phenomena observed in the natural world.”

Stated in another way, a hypothesis is an explanation based upon and about an observed natural phenomenon. However, what exactly is a natural phenomenon in relation to natural science? According to the Next Generation Science Standards (NGSS), a natural phenomena is defined as “observable events that occur in the universe and that we can use our science knowledge to explain or predict.”

This definition by the NGSS was developed from a 26 state effort that created new education standards in science in collaboration with the National Science Teachers Association (NSTA), the American Association for the Advancement of Science (AAAS), the National Research Council (NRC), and the nonprofit organization Achieve.

Supporting the NGSS definition of natural phenomena as being observable events are various philosophers of science, such as Ian Hacking, considered the first to define phenomena from the scientists perspective, who stated that a phenomenon is “commonly an event or process of a certain type that occurs regularly under definite circumstances.

The word can also denote a unique event that we single out as particularly important.” Michela Massimi, another philosopher of science, agreed with Hacking in her book Perspectival Realism, stating that “phenomena are events: they are not things, entities, structures, facts, or states of affairs.”

Thus, from these definitions, we can narrow down natural phenomena to observable events (or processes). Nonetheless, not just any event will do. In order for a phenomenon to be natural, these events must occur in nature without human influence and interference. In other words, the events are not man-made.

If these conditions are met and a natural phenomenon is observed, a proposed explanation can be formulated in order to try and describe what might be occurring.

The Britannica goes on to state that two very important and primary features of a scientific hypothesis are falsifiability and testability. Falsifiability means that the hypothesis is stated in such a way that there is some capacity to be able to prove the hypothesis wrong through experimentation.

This idea was introduced by scientific philosopher Karl Popper in 1935 in his book The Logic of Scientific Discovery. According to this concept, someone should be able to conceivably design an experiment that could prove the hypothesis wrong. If a hypothesis is capable of being proven wrong, and yet it is supported by experimental evidence of its truth, then it can be considered as a scientific hypothesis.

A falsifiable hypothesis should be formulated as an “If…then” statement that summarizes the idea established from the phenomenon, and it must have testability, meaning that it can then be supported or refuted through experimentation.

The observation of a natural phenomenon and the creation of a falsifiable and testable hypothesis is the first part of the scientific method, as noted in Chapter 2 ~ Science as a Way of Understanding the Natural World of the book Environmental Science.

“The scientific method begins with the identification of a question involving the structure or function of the natural world, which is usually developed using inductive logic (Figure 2.1). The question is interpreted in terms of existing theory, and specific hypotheses are formulated to explain the character and causes of the natural phenomenon.”

“In contrast, a hypothesis is a proposed explanation for the occurrence of a phenomenon. Scientists formulate hypotheses as statements and then test them through experiments and other forms of research. Hypotheses are developed using logic, inference, and mathematical arguments in order to explain observed phenomena.”

According to Elsevier, a Dutch academic publishing company specializing in scientific, technical, and medical content, without a hypothesis, there can be no basis for a scientific experiment. We can therefore conclude that the hypothesis is crucial to obtaining scientific evidence.

They state that the hypothesis is “a prediction of the relationship that exists between two or more variables.” What this means is that a hypothesis must be designed and written in such a way as to “prove” whether or not a predicted relationship derived from the natural phenomenon exists between two variables: the independent variable (the presumed cause) and the dependent variable (the observed effect).

This is usually then stated as the null hypothesis, which predicts that there is no relationship between the variables, and as the alternative hypothesis, which predicts that there is a relationship between the variables.

Once the hypothesis has been established, a proper experiment can be designed in order to test it. According to American philosopher and historian of science Peter Machamer in his 2009 paper Phenomena, data and theories: a special issue of Synthese, the experiment should show us something important that occurs within the real world. The goal is to ensure that the aspects of the observed natural phenomenon that originally sparked the hypothesis are “caught” in the design of the experiment.

In this way, the experiment will be able to tell us something about the world and the phenomena studied. Thus, it is critical that the hypothesis is tested properly through an experimental design that accurately reflects the observed natural phenomenon and what is seen in nature.

Does the experiment actually show us something important about what is going on in the real world that lies outside of the experimental setting? One form of this worry is gleaned by making a distinction between phenomena and artifacts (see Feest 2003, 2005, 2008). This problem arises when operationalizing a phenomenon so it may be experimentally investigated in a laboratory or other non-natural setting.

Basically, we want to make sure that when we create an experimental design, we are reasonably sure that we are ‘catching’ the aspects of the phenomenon that originally sparked our interest or which we were seeking to explain. We want our experiments to tell us something about the world, about the phenomena. 

When we design experiments we try to simplify situations so that we may control the relevant variables, which will then allow us to intervene and observe what happens as a result of the intervention. We design experiments to generate data, which then may be used to tell us something about how the world is or how it works. But often we know something about the phenomenon of interest before setting up the experiment.”

If the hypothesis is tested correctly through proper experimental design via the scientific method, and repeated testing strengthens the correlation between two or more things happening in association with each other resulting in the observed natural phenomenon, the cause of a natural phenomenon can be proven.

This would make it possible to determine the likelihood of the event happening again. If the results are confirmed through replication and reproducibility by independent researchers, this gives the hypothesis predictive power. Once the predictions provided by the hypothesis are repeatedly confirmed through independent verification and validation by the scientific community, the hypothesis can then be elevated to a scientific theory.

However, to get to the point of becoming a scientific theory, the hypothesis must be confirmed through accurate experimentation first, and it must not be falsified.

This absolutely critical fact is seemingly something that was forgotten when the germ hypothesis was elevated to the status of a scientific theory. As Albert Einstein stated, “No amount of experimentation can ever prove me right; a single experiment can prove me wrong.”

What does it say about the evidence supporting a hypothesis if the experiments designed reflecting the hypothesis failed, and the evidence obtained that “supports” it was through experiments that were not designed properly and do not reflect the proposed explanation?

If the experiments do not reflect the hypothesis that was derived from the observed natural phenomenon, can the knowledge acquired still be considered scientific knowledge that tells us anything truthful about what really occurs in nature? With these questions in mind, let’s see if Louis Pasteur’s hypotheses hold up under scrutiny.

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