There was a great response to my first post in this series, so thanks to everyone who contributed to that. For my second one I’ve decided to tackle an issue that’s quite crucial to how Critical Thinking relates to the Middle Way.
There are two types of argument, normally known as induction and deduction. Deductive argument is what is classically formulated as argument and abstracted into logic. Deductive argument begins with assumed claims known as premises, and draws a conclusion from those premises. Within the terms of interpretation and the beliefs it assumes, the logical link between the premises and conclusion in deductive argument is absolute. If the premises are correct, then the conclusion must be correct if the reasoning is valid (i.e. follows the laws of logic).
All engineers are human beings.
So John must be a human being.
This valid argument must be correct if John is indeed an engineer, and if indeed all engineers are human beings. But I might have false information about John, and robotic engineers may be under development right now in Japanese laboratories. My assumptions may be false, but if they happen to be true then the conclusion must also be true.
That’s what we’re traditionally told about deductive argument. However, if you take into account embodied meaning, then we are all also going to have slightly different meanings for ‘John’, ‘engineer’, ‘human being’ etc. experienced in different bodies. It’s only if we further assume that these meanings are sufficiently shared and stable that a deductive argument can be ‘valid’ in this way.
The other type of argument, however, is far more common and far more useful. Inductive argument is imperfect argument that begins with limited information and draws further conclusions from it. Sometimes such reasoning can sometimes be grossly over-stated and prejudiced. For example:
My neighbour was burgled by a man from Norfolk.
Norfolk people are all criminals.
This is a crude example of prejudiced reasoning. It takes just one example and draws a conclusion about a whole class of people that are extremely varied. It’s obviously not taking into account all the reasons why it might be wrong.
However, inductive reasoning is what we rely upon constantly. If we take into account its limitations it can be a justified way of reasoning. For example:
Tom has failed to fulfil his promises to his mother on ten successive occasions within a month.
His mother should not place any further reliance on Tom’s promises.
It’s still possible that Tom is trustworthy, and has just had ten unfortunate sets of events that stopped him fulfilling his promises, or that he was at fault in the past but has now completely reformed. However, it’s unlikely. We are usually obliged to trust the weight of our experience in cases like this. We could have confidence in the conclusion here as long as we also took into account the possibility that we could be wrong.
So, my argument here is that deductive argument, though perfect in theory, is not really different from inductive in the way we should treat it in practice. Deductive logic, though it may be perfect in the abstract, is in practice dependent both on the assumptions made and on the interpretation of the words of the argument to be applied in our lives. In practice, then deductive reasoning is just as fallible as inductive. If we use inductive reasoning with awareness of its limitations, though, it can provide us with justified beliefs. This kind of reasoning is justified because of its fallibility, not in spite of it.
How well justified are the following (inductive or deductive) arguments?
1. The no. 37 bus that I take to work has been more than ten minutes late on three successive days. This is an unacceptable standard of punctuality, and it has made me late for work. I shall write to the bus company to complain.
2. If the UK economy continues to grow at the rate it managed during the last quarter of 2013 (a rate unmatched since the crash of 2008) then we can conclude that economic recovery is well under way.
3. Romanians in the UK are arrested at seven times the rate of Britons (Daily Mail), so if more Romanians come to the UK we can expect an increase in crime.
4. If God exists and God is good, he would not allow people to suffer without making the truth available to them. So he must have sent divinely-inspired prophets to guide people.
5. I’ve been practising this difficult piano piece for two months now, but I seem to be making no progress. I keep making the same mistakes. I should give up this piece and learn something else.
Picture: Engineer at work by Angelsman (Wikimedia Commons)