Reference no: EM132507905
Assumption-spotting is perhaps the most crucial practical skill in Critical Thinking. The key issue here is whether what you think may be an assumption is actually necessary to the argument. If you assume that someone is making an assumption that they are not making, then obviously this is unfair. If an assumption is present, then it would have to be true for the conclusion to be true. For example:
John is out.
His coat is missing from the peg.
Here, it is being assumed that John must take his coat when he goes out. It is also being assumed that he only has one coat, and that the coat is not missing because someone has stolen it, or for some other reason.
However, if someone were to claim that "John is a man" was an assumption here, this would be incorrect. "John is a man" is a possibility, but it is not an assumption that the conclusion relies on: John does not have to be a man for the conclusion to be correct. John could be an alien or a polar bear and the conclusion would still be fine.
Assumptions can be classified into explicit and implicit types. An explicit assumption is one that is stated in the argument: in the above example, this would be "His coat is missing from the peg." We assume the accuracy of this information in the argument. Implicit assumptions are not stated, but nevertheless must be true for the conclusion to be true. So, in the above example "John must take his coat when he goes out" is an implicit assumption required to reach the conclusion.
Some assumptions are more immediately important in the context than others. "The universe exists" is a background assumption in almost all arguments, but not one we need bother discussing most of the time. When you are identifying assumptions, pay the most attention to those stated or unstated beliefs that are required in order for the conclusion to be true.
Identify the assumptions in these arguments. If possible, distinguish between explicit and implicit assumptions.
1. The upper decks of double-decker buses are best avoided. I've often found them to be full of rude teenagers playing loud music with no concern for the feelings of other passengers.
2. The 2003 invasion of Iraq was illegal because it was motivated only by a desire for oil.
3. Natalie had better watch out! There's a polar bear behind her!
4. Since there has been no snow in southern England so far this winter and it's now the middle of January, we can conclude that it will be a mild winter throughout the UK.
5. Richard III's body was found under a car park in Leicester, and he fell in battle nearby in Bosworth Field, so it is only right that he should be re-buried in Leicester.