128 Unit 4 Applied critical thinking
Why do we use the word ‘safe’?
The practice of calling some inferences unsafe
is a recognition of the importance of
reasoning carefully. What makes an inference
unsafe is not just that it may be wrong, but
that it may have consequences, sometimes
very serious ones. Perhaps the most obvious
illustration is a criminal trial, where a verdict
must be reached on the basis of the evidence.
A trial-verdict is a particularly serious kind of
inference, on occasions a matter of life or
death. As the result of a faulty inference, an
innocent person might go to prison for a long
time. On the other hand, a not-guilty verdict
passed on a guilty person may leave him or her
free to commit a further atrocity. You will
sometimes hear the expression, ‘That’s a
dangerous inference to make!’ We can easily
see why that is entirely appropriate.
But even if there are no obvious dire
consequences, it is still important to reason
well rather than badly, because it gets us closer
to the truth. Judging when an inference is safe
or reliable is therefore a key element in critical
thinking.Assessing inferences
With this in mind, read the following passage
(Doc 2) and make a mental note of the
information that it contains. It introduces a
topic which will occupy the rest of the
chapter, and feature in the next two.http://www.CartoonStock.comwarm phase, coinciding with a particular
alignment of the Earth and Sun, is far from
adequate to justify an out-and-out prediction
that the present interglacial will also last that
long. No serious scientist would go so far. The
author of the Geological Society webpage
from which the information is Doc 1 was
sourced claims only that:
F On these grounds, even without human
intervention, another 20,000 years of
warmth may be expected.Compare this with C. Although it is drawing
broadly the same conclusion, it expresses it in a
careful way which would permit its author to
fend off objections. Another 20,000 years may be
expected, on the evidence supplied. That claim
does not cease to be true, at the time of making
it, even if in 10,000 years’ time it turns out to
have been optimistic. Nor will F be falsified if
new, contrary evidence comes to light, because
the author has qualified the claim by prefacing it
with: ‘On these grounds.. .’ You should
remember these details of presentation when
you are constructing your own arguments. They
may seem like purely linguistic points; but they
can make the difference between inferring
something that can be substantiated, and
something that cannot.
Whoever inferred D has taken the right sort of
care in expressing it. It is preceded by the phrase:
‘According to the recent geological record.. .’
and draws a conclusion that the record firmly
supports. Recent ice ages (geologically speaking)
have lasted between 3 and 17 times longer than
interglacials. So glacial conditions have been the
prevailing ones during that period, and it is the
Earth’s present climatic state that is unusual. D is
a safe inference.
For E to be true it would mean that the
standard view was correct after all, and/or that
the trend of the last three glaciation cycles was
continuing. It would also require global warming
to be taking place; and to be capable of delaying
the onset of an ice age. E is not impossible, but
it would take a lot more than the claims in Doc
1 to make it true. In a word, it is unsafe.