PHL145H5 Chapter Notes - Chapter 5: Liniment, Scotiabank, Jargon
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Chapter 5 Textbook Notes
5.1: Other People As Sources of Information
Almost everything we know is based oﬀ of information we’ve learned from others,
either from seeing, hearing or reading.
5.1.1: Information: We Need Something To Reason About
Testimony bears on reasoning for two closely related reasons:
The premises of our reasoning is often based on the things we’ve learned
We frequently require background information in order to verify whether
the premises of an argument are plausible and whether some relevant and
necessary information has been omitted. We often rely on others for this
Many of our premises are based on the claims of others.
E.g. If the city was to build a toxic waste near your neighbourhood, you would
most likely have a problem with it.
Your argument against this and your premises would be based on the
claims of researchers and experts regarding the dangers and risks about
We must always ask the three questions when given an argument:
Do the premises support the conclusion?
Are the premises plausible?
Has any relevant information been omitted?
E.g. Suppose when you have a kid, your neighbour tells you not to let them
watch TV because your kid will end up being dumb.
You must do research to whether argument is valid.
The information you research is the work of others, you must be able to
determine the reliability and validity of the sources you use.
We must be able to distinguish between:
Experts and Self-Styled Experts (People who think they know more than
they actually do)
Experts with a bias and Experts with no bias
We must also be able to determine when a ﬁeld has no expert, and in this
situation, what must we do?
At the end of the day, we must be able to determine the experts we chose to follow.
Sometimes, experts may have conﬂicting opinions, this is where it comes down to
personal judgement with who you choose to believe.
5.2.1: What Is An Expert?
An expert/authority is someone with a large knowledge about a particular ﬁeld.
The terms “expert” and “authority” will be used in a broad sense so that we can
consider a vast amount of sources of information as potential authorities.
In this sense, authority doesn’t refer to someone in charge, but rather to
someone who is knowledge about a certain ﬁeld.
Sometimes experts may be an expert in a skill that is diﬃcult to describe.
E.g. A doctor may have seen a certain illness so many times, they have
become an expert in detecting that illness. They may have trouble
explaining how they know, but if they are usually an expert, they are
considered an expert.
Two important facts about experts:
Experts do not always have to be correct.
Experts are still human beings, they are still bound to make an error
at some point or another. If they had to be correct every time, the
world have no experts since everyone makes mistakes.
You are still better oﬀ relying on an expert than someone who is not
E.g. Suppose an expert is correct 60% of the time and a non-
expert is correct 50% of the time, who would you choose to
Experts come in degrees.
There can be someone who is more of an expert than someone
else, but both people can still be considered an expert.
E.g. A dentist of twenty years is probably more
knowledgeable about teeth than someone who just
graduated from dentistry school, regardless both are still
For less diﬃcult jobs, the graduate is more than capable of
completing the job easily.
5.2.2: Field Of Expertise
An person can only be considered an expert within they ﬁeld of expertise.
E.g. A pharmacist is in an expert in medicine, but is not an expert in
An expert in one ﬁeld probably knows as little as everyone else about
No one is an expert in every ﬁeld.
5.3: Evaluating Claims To Expertise
When we cite an expert in one our arguments, it is very important that we remember
that these types of arguments are never deductively valid.
The reason is that even the best, most intelligent experts in their ﬁeld make
mistakes or are incorrect from time to time.
Instead, we will often consider the argument to be inductively strong.
The more experts that agree on something, the stronger the argument is.
When evaluating the claims of experts, it is very important the we consider the
1. Do we care enough about the issue to evaluate those who claim to be experts
on the topic?
Often times the issue we are curious doesn’t concern us enough to justify