Strength is a function of the gap between premises and
conclusion: The larger the gap, the weaker the argument. It
is always possible to narrow the gap by introducing a new
A strong argument has a small gap between the stated premises
and the conclusion, and the gap can be filled by a fairly
innocuous premise that would be easy to defend.
A weaker argument has a larger gap, which could be filled only by
a more substantial premise that would be harder to defend.
A thoroughly weak argument has a huge gap, which could be filled
only by a premise that is obviously false.
So we can measure the gap, and thus determine the argument's
strength, by seeing what sort of premise it would take to fill
According to de Tocqueville's argument about democracy:
The people serve on juries. Therefore, the people control the
To say that the people control the government is to say that they
control the government's actions--that they have some influence,
direct or indirect, on everything the government does. When they
serve on juries, the action they control is the action of
punishing criminals. So to make the above inference strong, we
need the assumed premise that punishing criminals is the only
action government takes, or at least the main one. This is a
dubious assumption, to say the least. After all, governments wage
war, impose taxes, regulate the economy, and do many other things
in addition to punishing criminals.
The need to make such a dubious assumption confirms our sense
that the argument from 2 to 3 is very weak indeed.
When we evaluate the argument as a whole in light of the
components, there are some principles to follow.
Let us examine each of these in turn.
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