The philosopher David Hume, defines two main types of reasoning.
Deductive Reasoning and Inductive Reasoning.
For Hume, all true reasoning is the deductive kind.
Deductive Reasoning is based on purely observable fact.
Facts alone with nothing added.
The other kind, Inductive Reasoning, is when we infer something that isn’t actually there.
For Hume, Inductive Reasoning is fallacious and misleading.
And yet most of our thinking, Hume says, is based on Inductive reasoning.
I think we can learn a lot from this.
So let’s start by following Hume’s thinking, as I see it.
Hume says the only true reasoning is Deductive Reasoning.
We might also call this ‘reductive’ reasoning.
We reduce everything down to the exact truth of what is observed.
And nothing more.
And that’s the most important part: “nothing more”.
We don’t add a single thing.
However, most of our thinking is based on Inductive Reasoning.
We can call this ‘assumptive’ reasoning.
Hume calls it ‘cause-and-effect’.
We assume a cause-and-effect relationship where we have no proof.
Hume’s example is billiard balls.
Ball A strikes ball B, and ball B moves.
We assume that ball A striking ball B, has caused it to move.
But actually we didn’t observe this and can’t prove it.
We observed a ball striking another ball.
We observed the second ball moving.
We didn’t actually observe a link between the two events.
We assume it, we infer it.
This is Inductive Reasoning.
For Hume this is like superstition.
Something we believe to be true even though we can’t prove it.
Hume says this leads to generalisations and sloppy thinking.
Well that’s true.
That is one aspect of it.
But there’s another.
For me Deductive (reductive) Reasoning is inward facing.
It looks at the single final truth.
What it actually means.
The more limiting the better.
Inductive (assumptive) Reasoning is outward facing.
It looks at the interesting possibilities.
What it could mean.
The less limiting the better.
Deductive Reasoning is about facts.
Inductive Reasoning is about opportunities.
And there’s real value in separating thinking along Hume’s lines.
Not to decide which sort of thinking is right?
But which is right in different circumstances?
When do we need to close down the thinking?
When do we need to open it up?
But we don’t differentiate between different types of thinking.
So we use the wrong thinking in the wrong place.
These two types of thinking do different jobs and have different uses.
For instance.
Deductive Reasoning might be perfect for defining the business problem, for identifying the target market, distribution and cost issues, for all kinds of decisions about where we’re at, right now.
But Deductive Reasoning can’t tell us where to go in the future.
By it’s very nature, Deductive Reasoning isn’t about vision.
It’s about fact.
So it’s about the present and the past.
Not about the future.
What has happened, not what could happen.
The past is about Deductive Reasoning.
The future is about Inductive Reasoning.
There’s a great value in recognising the need for both types of thinking in marketing and advertising.
The security blanket is Deductive Reasoning.
But the trap is, that will keep us stuck where we’ve been.
Deductive Reasoning may be great for identifying the problem.
But it’s exactly wrong for telling us what to do about it.
For that we need Inductive Reasoning.
Reasoning based on possibilities, probabilities, inferences and assumptions,
Exactly the kind of reasoning Hume thought was wrong.

But I would say that.
In my job we can only operate on Inductive Reasoning.