young cat pouncing on an insect

Cats eat mice — Is this evidence or inference?

We know that cats eat mice because we all watched Tom & Jerry cartoons. But how do you know for sure if the cat killed the mouse?

You wake one morning to find a dead mouse on the kitchen floor just below the cat flap. Nearby the family cat is carefully cleaning a paw in a way that only a cat can. 

You scold the cat for doing what it does best and gingerly drop the dead mouse into the bin.

A few days later, you are quietly eating your morning muesli with pot set yogurt and, through the cat flap, plops the family cat with another dead mouse held firmly in its canines. 

Again you scold the cat who looks incredulous at your perverse logic.

These events pale into insignificance against what happens the next day. 

When curled up watching your fourth episode of Succession for the evening, a mouse saunters across the hearth and in a flash, the cat is on it. Crunch and a drip of red falls onto the carpet.

Cats eat mice

You have known since kindergarten that cats are predators and that, at least, mice and rodents are prey for small felines in the wild. So the default position in your mind is that the cat has killed the mice.

The inference in the death of all three mice is that the cat did it.

But let’s look a little more closely.

Wriggle room 

Only in the last instance, where you saw the cat lift out of her lethargy and grab and kill the mouse, do you have objective evidence. Your eyes gave witness to the event.

The cat cleaning a paw with a mouse on the doormat is circumstantial. The evidence is a dead mouse in the vicinity of a cat. Maybe the cat killed the mouse, but you have no certainty.

In the second incident, the evidence is a cat with a dead mouse between its whiskers. It is telling but not confirmation of predation. The feline could have picked up a mouse in the backyard that died of a heart attack.

Inference means reaching a conclusion based on evidence and reasoning. Cats are known to catch mice. There is a dead mouse on the doormat. The cat is nearby and looks smug.

Evidence is the available facts or information that indicates whether a belief or proposition is valid. You saw the cat pounce on the mouse in the living room with your own eyes, heard the crunch, and had to clean the stain on the carpet.

The difference is essential. 

Evidence is information in context and becomes irrefutable because of our rules on what constitutes evidence. Eyeballs don’t lie (usually).

Inference requires reasoning, the use of logic to conclude. There is a chance that inference reaches more than one conclusion depending on who makes the inference. And here, there is wriggle room because not everyone will apply logic in the same way.

black cat with yellow eyes on a couch
Photo by Ergita Sela on Unsplash

Both evidence and inference are helpful

It would be wonderful to have evidence to support all the complex decisions individuals and society must make, especially regarding food, the environment and our use of resources.

Whilst there are evidence gaps, typically there is more evidence available than is used for these choices. 

Instead, access, interpretation and overwhelm limit the use of evidence. It takes time and skill to source and filter all the details; time becomes a luxury when the world is warming and people are starving or obese. We also have a skills shortage. Not enough people know how to evaluate evidence needed for feeding everyone well.

When making any decision over food, from what you choose to eat to global food security, the recommendation should always be to make the time for evidence.

Where evidence is absent or hidden away in the archives, then decisions must use inference. It is better to make some logical calls and predict the likelihood of the cat having preyed on the mouse even if there is no proof.

The recommendation in the absence of evidence would be to use inference to guide decisions.

The proviso is that the cat might not have done it. Inference requires more caution than evidence.

Inference is the world of likelihoods. 

Don’t use hearsay instead

The reality is that both evidence and inference take resources, skill and healthy scepticism. All three of these are in short supply.

The temptation is to skip evidence and inference to use hearsay.

Gran said that the cat did it because her friend Doris saw a cat do that very thing in the summer of 1942.

This is silly, but evidence decisions are often made precisely this way.

What sustainably FED suggests…

Know the difference between evidence and inference and learn to recognise which one is in use for decisions that matter.

Inference always comes with a likelihood qualifier, it might have happened. 

Evidence is factual. 

And despite what the politicians might say and their PR people claim, there is no such thing as an alternative fact. Just a fact used out of context. But that is another post.

Check out how easy it can be to use evidence with our Evidence Reviews

Hero image from photo by Dorothea OLDANI on Unsplash


Mark is an ecology nerd who was cursed with an entrepreneurial gene and a big picture view making him a rare beast, uncomfortable in the ivory towers and the disconnected silos of the public service. Despite this he has made it through a 40+ year career as a scientist and for some unknown reason still likes to read scientific papers.

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