68 Unit 2 Critical thinking: the basics
opposite assumption that no one has the right
to own a piece of land and keep others from
using it, especially a large estate like the
Steinbergs’. Many people seriously question
the assumption that trespass is morally (and
not just legally) wrong, or that trespass laws are
just laws, or that anyone needs ‘permission’ to
set up a home where they choose. One might
argue that the Steinbergs showed a complete
lack of compassion in prosecuting the family:
that they used their money and power to evict
underprivileged people, of minority ethnic
status, for no obviously good reason other
than exercising their legal right. Some might
say that the Steinbergs have everything to be
ashamed of, and certainly much more to be
ashamed of than the travellers.
How you evaluate and respond to an
argument like this depends very much on
your own political and cultural assumptions.
But whichever side you take on the issues,
you will not have dealt critically with the
argument unless you have recognised and
given thought to these assumptions as well as
the explicit premises.The fact that the author assumes all this
rather than stating it, or offering any argument
for it, indicates that he or she simply takes it
for granted, and no doubt expects that many if
not all readers will do the same. In the culture
to which the author belongs there are laws that
protect property and punish trespass, and the
majority accept such laws because it is in their
interests to do so. Laws that prevent travellers
from setting up home wherever they like also
prevent them from moving into your house or
setting up camp in your front garden.
Consequently, people who own or rent homes
of their own tend to accept such laws, and
assume they have some moral backing, even if
at times they seem harsh. The author does not
see any need to spell all this out or argue for it.
It ‘goes without saying’.
But that doesn’t mean the argument or its
assumptions cannot be challenged. Not every
social group adopts the same attitudes to
private property as the author. There are
people who choose to live, or would prefer to
live, nomadic lifestyles without permanent
homes, who might start from the entirelySummary
• An assumption, under the ordinary
meaning of the word, is a claim or belief
that is presumed true, without necessarily
being warranted or justified.
• The premises of many arguments are
assumptions. In other words the conclusion
of an argument often rests on one or more
assumptions. If the assumption can be
shown to be false or unwarranted, then the
argument must be judged unsound.• Some assumptions that are made in the
course of an argument are implicit rather
than openly stated.
• Calling a claim or belief an assumption
means that it is questionable, open to
challenge, or in need of justification. It
does not mean that it is necessarily false
or unacceptable.
• Some assumptions reveal deep-rooted
beliefs or attitudes.