A theory is either true or false. Galileo's observations of

Hi,

Let me share my two cents here.

The question stem requires us to look for the questionable assumption made by the argument.

Let’s first try to deconstruct the argument:

What is the conclusion here?

Galileo’s observations of Jupiter’s satellites proved the truth of the Copernican theory.

What is the basis of this conclusion?

1) A theory is either true or false. Ptolemaic theory is shown to be false.

2) Copernican theory of planetary motion is inconsistent with the Ptolemaic account,

Thus, the argument concludes that Copernican theory is true because it is inconsistent with Ptolemaic theory which is false.
Let’s take an example:

If I say that XYZ flower is red and you say that XYZ flower is blue.

Now, we are inconsistent. Right? But if I am proven wrong i.e. the flower is not red, does that mean that you are correct i.e. the flower is blue? No. The flower could be pink or purple or any other color.

Thus, it is possible that though your answer is inconsistent with mine, it is also wrong.


Similarly, it’s possible that though Copernican theory is inconsistent with Ptolemaic theory, it is also false. However, the conclusion states that Copernican theory is true and thus the in-built assumption of the argument is that if two theories are inconsistent with each other, both of them cannot be false.

With this understanding, let’s look at the option statements:

A. whoever first observed something inconsistent with the truth of the Ptolemaic theory should be credited with having proved that theory is false

This statement discusses who should be given the credit to prove that Ptolemaic theory is false. We are given Ptolemaic is false. Who should be given credit is not the focus of the argument. Thus, this choice is incorrect.

B. there are some possible observations that would be inconsistent with the account given by the Copernican theory but consistent with the account given by the Ptolemaic theory

This statements talks about the observations that would be inconsistent with Copernican theory but consistent with Ptolemaic theory. However, we are only concerned with Galileo’s observations in this argument, not other observations. Thus, this choice is an irrelevant and incorrect choice.

C. the Ptolemaic and Copernican theories, being inconsistent, cannot both be based on exactly the same evidence

This statement is about the basis of both the theories; however, whether or not these theories are based on the same evidence, the conclusion of the argument is unaffected. In the argument, we are concerned about the impact of one set of observations on the truth of these theories; we don’t know the original basis of any of these theories. Therefore, basis of the theories is not relevant to the argument. Thus, this is an incorrect choice.

D. numerous counterexamples were necessary in order to show the Ptolemaic theory to be false

We know from the passage that Galileo’s observations showed that the Ptolemaic theory is false This option tells us that it required numerous counter examples to show this result; however, our task is to look for the assumption that the argument makes while drawing the conclusion about the truthness of Copernican theory. Thus, this choice is incorrect.

E. the Ptolemaic and Copernican theories, being inconsistent, cannot both be false

This option identifies with our pre-thinking. The argument fails to consider that despite being inconsistent, both the theories can be false. This choice states the built-in assumption of the argument.

If we negate this option we get,
the Ptolemaic and Copernican theories, being inconsistent, can both be false

It shows that Copernican can be false, even if it is inconsistent with Ptolemaic theory. As we can see this breaks down the conclusion, this is the correct choice.

Ans is E.

Hope this helps!
Dolly