Motive vs. intent: Why the difference matters in design detection

There is an interesting discussion going on at "How do you prove purpose" at the far right.

One question that commonly arises when people discuss design in the universe is "how can you tell it is design if you do not know the motive of the designer?" Or perhaps the "purpose" of the designer?

Actually you can. The police do it every day in criminal investigations.

For one thing, there is a difference between motive and intent. Confusion on that subject can sometimes result in confusion about detecting design.

Legal cases typically turn on intent, not motive.

Here is an example: Harry and Jack are having a somewhat tense conversation over a beer and steak at the local pub.

Harry seizes a steak knife and tries to plunge it into Jack's ribs.

Pub regulars overpower him and the police are called. He is charged with assault with a deadly weapon.

That's intent.

No one knows his motive, but no one needs to know his motive. What he intended was obvious. And it is a crime.

A later investigation may turn up a motive - perhaps Jack had informed Harry that he was very friendly with Harry's girlfriend, and becoming more so all the time - and that it would be best if Harry would just disappear at this point.

But what if the investigation doesn't turn up a motive? What if Harry steadfastly refuses to say what they talked about?

For that matter, what if Harry doesn't know his own motives very clearly? He might be the sort who mumbles, "I never liked that guy. And then one day I just got really mad."

That's not insanity. He will probably be convicted on intent. It's the intent that shows design - the pattern of actions or events.

Design, in these matters, is inferred from a pattern of actions or events, not the detection of motive.

Whenever we can, we like to know the motive, but it is not essential for determining design.