I previously posted the difference between the two types of logical argument in the context of profiling.
But I'll summarise the difference briefly.
Imagine there exists two arguments one is deductive the other inductive:
Example Deductive Argument:
P1) All forensic psychologists love to read
P2) Bill hates reading
Conclusion: Therefore, Bill is not a forensic psychologist
So if we ignore whether P1 and P2 are actually true, if we say for argument that they are, then the conclusion 'Bill is not a forensic psychologist' has to be true. As long as we accept the premises as true then it's impossible for the conclusion to be false.
Example Inductive Argument:
This example comes from a great book by Peter Smith 'An introduction to formal logic'
P1) The cup of tea that I am drinking tastes the same as all the other cups of tea I have drunk before.
P2) All previous cups of tea have not killed me
Conclusion: This cup of tea is safe to drink
At first glance this may seem safe and indeed we rely on this sort of logic everyday. But it is not deductive: consider the scenario that someone for unknown reasons has slipped into our cup of tea a tastless, odourless poison.
Just because prior cups of tea were safe and they resemble this cup of tea, does not necessarily mean that this cup of tea is safe to drink.
What we can say is that the conclusion could still be false with true premises
A note:
Inductive reasoning is not bad reasoning, we rely upon it every day and it works. It's just not bulletproof logic.
A good example comes from Bertrand Russell on logic:
Imagine a chicken observes a farmer coming to feed it every day. One day the chicken sees the farmer coming to feed him, only this day is the day the farmer kills the chicken.
To conclude:
In a deductive argument, the conclusion has to follow from the premises. If the premises are true then it's impossible for the conclusion to be false.
In an inductive argument, the premises might be true, but the conclusion may still be false.
For a broader look at this as it applies to profiling see my post:
I previously posted the difference between the two types of logical argument in the context of profiling.
But I'll summarise the difference briefly.
Imagine there exists two arguments one is deductive the other inductive:
Example Deductive Argument:
P1) All forensic psychologists love to read
P2) Bill hates reading
Conclusion: Therefore, Bill is not a forensic psychologist
So if we ignore whether P1 and P2 are actually true, if we say for argument that they are, then the conclusion 'Bill is not a forensic psychologist' has to be true. As long as we accept the premises as true then it's impossible for the conclusion to be false.
Example Inductive Argument:
This example comes from a great book by Peter Smith 'An introduction to formal logic'
P1) The cup of tea that I am drinking tastes the same as all the other cups of tea I have drunk before.
P2) All previous cups of tea have not killed me
Conclusion: This cup of tea is safe to drink
At first glance this may seem safe and indeed we rely on this sort of logic everyday. But it is not deductive: consider the scenario that someone for unknown reasons has slipped into our cup of tea a tastless, odourless poison.
Just because prior cups of tea were safe and they resemble this cup of tea, does not necessarily mean that this cup of tea is safe to drink.
What we can say is that the conclusion could still be false with true premises
A note:
Inductive reasoning is not bad reasoning, we rely upon it every day and it works. It's just not bulletproof logic.
A good example comes from Bertrand Russell on logic:
Imagine a chicken observes a farmer coming to feed it every day. One day the chicken sees the farmer coming to feed him, only this day is the day the farmer kills the chicken.
To conclude:
In a deductive argument, the conclusion has to follow from the premises. If the premises are true then it's impossible for the conclusion to be false.
In an inductive argument, the premises might be true, but the conclusion may still be false.
For a broader look at this as it applies to profiling see my post: