18 Unit 2 Critical thinking: the basics
often referred to as hypotheses, even when
they are generally accepted as true.
Take the prediction that, if a dart and an
empty drink can are dropped simultaneously
from an equal height (under ordinary
atmospheric conditions), the dart will land
first. This claim is made on the grounds that,
whenever two such objects are dropped, the
result is always the same – or always has been
the same – so that it is entirely reasonable to
expect it to go on being the same in the future.
The observed result is explained by the general
principle that thin, arrow-shaped objects
encounter less air resistance than bulkier ones,
allowing the former to accelerate more rapidly
under the same force (in this case gravity) than
the latter.The hypothesis has been so well tested that
the probability of such a claim ever being
wrong is practically non-existent. We call it a
‘hypothesis’, rather than an absolute
certainty, because conceivably the laws of
physics may not be the same in the far,
unknowable future, or in all possible worlds.
Besides, there have been many scientific
beliefs in the past that no one seriously
doubted, but that have had to be revised
because of later discoveries. One of the
best-known examples is the belief that the
Sun circled the Earth, or actually rose each
morning from beneath the Earth and travelled
across the sky. It was widely accepted by
astronomers before the time of Copernicus.
More recently, Albert Einstein’s claim thator is as yet unverified. For example, someone
might claim, at a certain time and place:
[D] There’s going to be a storm in the next
24 hours.If there is a storm within one day of the
sentence being spoken, then you can say,
looking back, that the prediction (or forecast)
was correct. But you cannot, even with
hindsight, say that the prediction was a fact
when it was made, because at the time of
making it, it was not yet known to be true.
Even when a claim cannot be made with
certainty, it can often be made with some
degree of probability. If you are playing a game
with five dice, and need five sixes with your
next and final throw, it is a fairly safe
prediction that you won’t win, because the
chances of throwing five sixes all at once are
very low. But it is not impossible. On average,
five sixes will come up once in every 7776 (6^5 )
throws. The claim that you will lose, therefore,
has a high probability of being a correct
prediction, but it is not a fact. Similarly, if
someone said after you had thrown (and lost):
‘I knew you wouldn’t win,’ you could correctly
reply (as a critical thinker): ‘You didn’t know it.
You predicted it correctly, that’s all.’Hypotheses
Strictly speaking, many of the claims that
scientists treat as fact should be understood
as probabilities of a very high order. These are