All arguments, whether inductive or deductive, begin with assumptions (also known as premises). An argument may be deductively valid (that is, if its assumptions are true then its conclusion must be true) but rendered irrelevant or unhelpful in practice by unacceptable assumptions. For example:
The Pope is a secret Hindu.
If the Pope is a secret Hindu, he can’t really be a Catholic.
Therefore, the Pope isn’t really Catholic.
This is all entirely valid: if the assumptions are correct, then the conclusion is too. However, the assumption that the Pope is a secret Hindu is, to say the least, implausible. An argument is only as good as its assumptions, and it’s important not to be seduced by the slickness or the complexity of an argument into taking its assumptions for granted. Unfortunately there are a great many philosophy books, for example, that I’m confident are not worth spending time reading because, although their arguments are rigorous, they are based on unacceptable (and to my mind, insufficiently examined) assumptions.
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 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, implicit, and background types. An explicit assumption is stated in the argument: in the above example, this is “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. “John has only one coat” is also an implicit assumption, but of a kind we would call a background assumption. It has to be correct for the conclusion to be correct, but it doesn’t play a direct role in the reasoning. Rather, it is taken for granted.
The distinction between foreground and background assumptions is not hard and fast – it will vary with the context. Some more sceptical types will be more inclined to question background assumptions than others! However, it is helpful to recognise that 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.
Exercise
Identify the assumptions in these arguments. If possible, distinguish between explicit, implicit and background 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. Naomi 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 nearby in Bosworth Field, so it is only right that he should be re-buried in Leicester.
Picture: Pope Benedict XVI by Agencia Brasil (Wikimedia Commons)
1. In this argument, the conclusion that the upper decks of buses be avoided uses the passive mood, delinking the personal experience of the proposer’s discomfiture (an implicit assumption that everyone shares it) from the conclusion’s universal application.
2. In this argument, the conclusion on the legality of war is based on an implicit assumption that wanting oil is against the law.
3. In this argument, the conclusion that Naomi ought to be wary is based on Naomi’s not being able to see what’s behind her, and the highly improbable background assumption that polar bears are commonplace visitors.
4. In this argument, the conclusion contains an explicit assumption that an absence of winter snow in southern England is a reliable indicator of a mild winter weather more widely. This seems a reasonable prognostication, given that background assumptions on the predictability of weather tend to weak.
5. In this argument, a conclusion on burial rights contains explicit assumptions that those rights are determined by the place of death, and where the body is found.
1. I think the first question is an implicit assumption but the argument is implausible, it depends on the time of day for example, the teenagers could be in school.
2. Here an explicit argument is made, the war is illegal, but the conclusion (it is illegal) may be true or not true, other factors may have been in play, regime change for example.
3. Here is a background (general) assumption, I think the assumption is irrelevant, polar bears can be dangerous, but who would allow a person to be close to a bear without taking precautions?
4. This is an explicit assumption, ‘there is no snow therefore it won’t snow’ but the conclusion of the argument is implausible, the vagaries of British weather!
5. This is an explicit assumption, ‘his body was found’ the conclusion or reason to keep his body there is implausible, by being a royal person many other factors are considered.
3. There’s an implicit assumption that, because Naomi has her back to the bear and can’t see it, she doesn’t know it’s there. Maybe she can hear it, smell it, or uses female intuition…..:) There’s a background assumption that Naomi is a human female, but she might be a sabre-toothed tiger or a wooly mammoth. There’s an implicit assumption that ‘behind her’ means in immediate proximity to her; but the polar bear might be many miles behind her.
You can tell I’ve acted in pantomime, Norma. “Oh no you’ve not! Oh yes I have…..”
Hi Peter, I like your pantomime phrase. Oh yes I must admit it doesn’t take much to make me have a rethink. So, ‘There’s a polar bear behind her’ is an implicit assumption of danger, would the conclusion that she should watch out be true and plausible – probably. I’m really not sure!
The argument is couched in language, as I see it, that is deliberately constructed for pantomime effect. It is stuffed with absurdities, it includes several assumptions (explicit, implicit and background ones) that – taken together cause such dissonance that they make on either scratch one’s head, or smile a crooked smile. In a pantomime situation, where one is already sensitised to the absurd, and disinhibited by having one’s thinking derailed, it would raise a laugh.
At least, that’s my crackpot theory…….
The pantomimic potential of no.3 hadn’t struck me before, but now I think about it, a lot of comedy in pantomimes does arise from the unquestioned assumptions of characters. The same applies to stage magic. There’s a video where the magician James Randi talks about this: http://www.youtube.com/watch?v=2qLwTPq-5uI .
Hi Robert, Thank you for the video, it is so true what James Randi says in such an amusing way, we have come to trust that certain actions we make will be safe. In order to function smoothly it seems that we have to be confidently trusting.
Thank you Peter, it is fun when our thoughts spin off at a tangent and land in new territory.
1. The implicit assumption here is that the other people would also want to avoid using the upper deck due to the circumstances described in the implicit assumpion. “I’ve often found them to be full of rude teenagers playing loud music with no concern for the feelings of other passengers” . There is another (background ) assumption that people would believe the frequency and accuracy of the explicit assumption.
2. The implicit assumption here is that wars are illegal if only motivated by desire for a natural resource such as oil. A background assumption is that wars should be legal.
3. There are implicit assumptions here that Naomi is a human being, that she is not visually impaired, that the polar bear is alive, not in a cage, dangerous or that Naomi doesn’t have a death wish.
4. The assumption here is that because the winter has been mild up to the middle of January, it will continue to be so. A background assumption is that England has a climate where snow is a likely occurrence in winter.
5. An implicit assumption here is that bodies should be buried near where they have been found. A background assumption is that the body should be buried and not cremated, frozen or put in a museum.
Here are my answers:
1. Explicit assumption: the second sentence
Implicit assumption: Places with rude teenagers should be avoided
2. Explicit assumption: The invasion was motivated by a desire for oil
Implicit assumption: Being motivated by a desire for oil makes an invasion illegal. (This doesn’t necessarily have to be generalised to other natural resources, Barry).
In context, Barry’s probably right that there’s a background assumption that wars should be legal: however, it isn’t actually stated that the war was wrong.
Norma – whether or not the conclusion is actually true isn’t relevant to what the assumptions are. It’s just about what would hypothetically have to be true for the conclusion to be true.
3. Explicit assumption: There’s a polar bear behind Naomi.
Implicit assumption: The polar bear provides a reason for Naomi needing to watch out (i.e. it is dangerous).
There are loads of background assumptions here, some of which Barry and Peter spotted: e.g. that the polar bear is alive, close behind, awake, not in a cage etc; also that Naomi doesn’t have a death wish, yes, or that Naomi is not protected by a cage or other barriers.
Some of the background assumptions suggested do not have to be the case for the conclusion to be correct. Naomi doesn’t necessarily have to be human : she just has to be vulnerable to polar bears. If she was a rabbit this would still be the case. It doesn’t make any difference whether or not Naomi can see the polar bear if “watch out” just means “be on your guard”. We also don’t have to assume that polar bears are commonplace.
4. Explicit assumptions: The first part of the sentence up to the comma
Implicit assumptions: That the mildness of the weather so far will continue for the rest of the winter. That the weather in Southern England is a guide to the whole UK. Barry’s also right about the background assumption.
5. Explicit assumptions: The first two phrases.
Implicit assumption: That where the body is found and where it originally died should determine where it is re-buried. A background assumption here is that there are no more important considerations that overrule this criterion.
Hi Robert, oh dear, I will keep trying to improve.
Hi,
I am a week behind, but I’ll have a go anyway.
1. There will be a lesser amount of rowdy teenagers on the lower deck of the bus. (I think that this is an implicit argument – possibly background, but I am not sure).
2. A war motivated only by a desire for oil is illegal (I think that this is explicit).
3. Polar bears are dangerous (implicit – changed from explicit).
4. The weather in southern England can be used to make predictions about the weather throughout the UK (Implicit – I think)?
5. Kings should be buried near where they have died. (Implicit).
That was tough!
Rich
Hi Rich,
1. The lesser amount of teenagers on the lower deck is a background assumption – one I failed to note above.
2. The war being illegal is the conclusion of the argument, not an assumption.
I’d agree with your other answers. More details in my post above.
Just checking to see if my students can respond to the questions here.
Anyone is welcome to respond, as long as the responses stay relevant! I won’t promise to spend time responding myself if you have lots of students, but you could always respond yourself, and my suggested answers are already given below.
R. Diya
Glades Central
AICE Thinking Skills
10th
1. “I’ve often found them to be full of rude teenagers playing loud music with no concern for the feelings of other passengers” is the explicit sentence because the assumption is stated in the argument.
Implicit assumption is when he said places with rude teenagers should be avoided.
2. Explicit : It the exercise, it stated that the invasion was motivated by a desire for oil.
Implicit: Although it is not being stated, what they implied was that being motivated by a desire for oil makes an invasion illegal.
1. This person assumes that the upper decks are full of rude teenagers this assumption is explicit. One thing that is implied that this person does not like teenagers. He assumes they are teens but they could be young adults. His past experiences with the upper deck have been with rude teenagers.
2. The explicit assumption is that the invasion of Iraq was driven by desire for oil. It was implied that the invasion was made by America. He assumes that because Iraq is wealthy in oil that is the only reason for the invasion. Then again who’s says that Iraq is wealthy in oil?
AICE Critical Thinking
Glades Central 9th grader
1. This person assumes that the upper decks are full of rude teenagers this assumption is explicit. One thing that is implied that this person does not like teenagers. He assumes they are teens but they could be young adults. His past experiences with the upper deck have been with rude teenagers.
2. The explicit assumption is that the invasion of Iraq was driven by a desire for oil. It was implied that the invasion was made by America. He assumes that because Iraq is wealthy in oil that is the only reason for the invasion. Then again who’s says that Iraq is wealthy in oil?
1. The explicit assumption is that the upper decks of the busses are filled with teenagers. An implicit assumption would be that they’re implying that they don’t like teenagers. Has he always experienced the rudeness of teenagers in past experiences? How do they know that they are teenagers? Did he do anything to provoke the “teenagers” and cause them to be rude?
2. The explicit assumption is that the war was caused due to the desire for oil. The implicit assumption is that Iraq was invaded by the U.S. How do we know that it was invaded the United States? How do we know Iraq was invaded only for oil purposes? It could’ve been invaded for other problems (economical, political, international commerce, etc.).
1. The explicit assumption is that the upper decks of the busses are filled with teenagers. An implicit assumption would be that they’re implying that they don’t like teenagers. Has he always experienced the rudeness of teenagers in past experiences? How do they know that they are teenagers? Did he do anything to provoke the “teenagers” and cause them to be rude?
2. The explicit assumption is that the war was caused due to the desire for oil. The implicit assumption is that Iraq was invaded by the U.S. How do we know that it was invaded the United States? How do we know Iraq was invaded only for oil purposes? It could’ve been invaded for other problems (economical, political, international commerce, etc.).
The assumption is that the teenagers have no concern for the feelings of other passengers. This is a background assumption because the author is using their personal experience. An alternate assumption, is that the upper decks are less full because of the loud music or people avoided the upper decks because it is not comfortable.
1.The explicit assumption to the question one is that the upper decks of double-decker buses are filled with rude teens. The implicit assumption is that he does not like teenagers because they are all rude. In his past experience he has found rude teenagers playing loud music, with no concern for the feelings of the other passengers.
1.) The explicit assumption is the upper deck of the bus is full of teenagers that are rude and loud. You can assume that this person does not like teenagers. He often found in his past experience that these teenagers had no concern for others feelings because they played loud music and didn’t take others into consideration. How does he know that the top deck is full of teenagers ? What if they were young adults?
2.) The explicit assumption is that the war was caused due to the desire for oil. The implicit assumption is that Iraq was invaded by the U.S. How do we know that it was invaded the United States? How do we know Iraq was invaded only for oil purposes it could’ve been invaded for other problems (economical , political , international commerce, etc.).
the assumption is that teenagers have no concern for the feelings of other passengers this is a background assumption because the author is using their personal experience an alternative assumption is that the upper deals are less because of the loud music or people avoided the upper decks because it is not comfortable
1. The explicit assumption is the first sentence stating that other people would want to avoid going the upper deck due to the situation pronounced in the implicit assumption. The second sentence is a background assumption, explaining why the top bunk should be avoided.
2. The explicit assumption is that war is illegal because it was only driven by a desire for a natural resource such as oil. The implicit assumption is that being driven by a desire for oil makes an invasion illegal.
E Rivera
Aice Critical Thinking
12
1] The first question is an implicit assumption because the person could have been bias to the teenagers, and the teenagers could have been going to a special event, or may they not be teenagers.
2] The second question is implicit assumption because the person never says why it is illegal, but only states that the war was motivated by oil.
C.Clark
Aice Critical Thinking
grade: 9
Glades Central hs
1)The person he/she who rode the bus that specific day could be bias against the teenagers because ,it could have been the bus playing the loud music ,Or even a special event happening at the moment.But that does not say that the teenagers are always on the upper deck.So this will be an implicit assumption.
2)This assumption would be implicit because the person is stating that the invasion of iraq was illegal but its not stating why it was they only say that it was motivated by a desire for oil , but not why it was illegal.
GladeCentralAiceCriticalThinkig9ThGrade
1. The first sentence is an explicit assumption and the last part is the background assumption, but there could be three questions asked: first of all, how does he know that the teenagers are rude, how does he know that that they have no concerns or feelings for the other passengers, how does he know that the people playing the loud music are teenagers he is stereotyping them.
2. The explicit assumption is that the war was motivated by a desire for oil. This could also be considered as a background assumption I say this because the war could have been about anything but they are giving you the extra information that will make you dig into the assumption about the war being illegal. I believe that the part where it said that “the 2003 invasion of Iraq was illegal” I believe that that will be a conclusion because when I first read it I was like this could be and explicit assumption then I was reading the other replies and i saw most of them was like it could be a conclusion and i went back and read it and it can really be a conclusion because they are saying that it was illegal that can either be true or false but nobody really knows, they are just assuming that it was motivated by the desire for oil.
1.We can assume that this person had a bad experience on the upper deck of a double-decker bus, assuming that what happened to this person would also happen to every passenger of the upper decks. But this claim is questionable in ways like who else was a passenger of the upper decks? did the teenagers bring their speaker on the bus? and how does this person know that these teens have no respect for the other passengers? making this assumption implicit.
2.Implicit: the assumption that oil was the motive of their invasion could or could have not been true in fact there may be other reasons for such invasion. And as i’ve seen before in other comments it being a illegal may or may not be true.
J.Simms
Glade Central Aice
9th
1. The implicit assumptions that is stated in this argument portrays the assumption that the writer thinks you should avoid the upper deckers of the the buses because these certain buses are full of disrespectful teeagers. The only problem is who is there to say that the “teenagers” on the bus were actually young adults.
2. The implicit information that was given is that the war was illegal because Iraq’s only intention for the war was to receive oil. My question is what if there was another motive for the war, what if they actually did it to help there country?
The first text is implicit and the second text is also implicit the reason being this is because we aren’t certain what the motive actually is.