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FIRST, IT WAS all about The Dress.

Now, it’s a cat.

The internet has again become embroiled in another violent debate over an optical illusion.

A 9Gag post asks readers if the cat is walking up or down the stairs. At the time of this post, almost 4,000 comments have been made arguing about the image.

“Down because generally the wood would be flat on the horizontal portion of the stairs and the stone is on the back/vertical portion of the stairs,” said one commenter.

“It’s clearly up, you just have to imagine the camera in a different angle,” said another.

The picture shows a cat with its paw out and tail up on a set of stairs. Depending on your perspective, you can either see the cat going down with the light coming from the ceiling, or up with the light coming from the downstairs floor.

Arguments for the cat going down include the pebbled texture of the stairs and what looks like a stair lip that would only be seen from an upward perspective (with the cat descending towards the viewer.)

The light would then be coming from the ceiling.

Some people are saying this is exactly how the stairs would look if the cat were going down. The arrow points to the stair lip, which wouldn't be visible from above.

An argument for up, however, insists that the stairs could be mosaic tile with a wooden lip, and the bright patch in the upper center of the image is light from downstairs. Viewers would then be looking down at the top of the stairs with the cat coming towards them.

Others are insisting the cat is going up, and the viewer is looking down at mosaic stairs with a wooden lip.

While many of the comments are hung up on the appearance of the stairs, there are some people who are wrapped up in the biology of the cat’s posture, insisting that this is exactly how a cat would look if they were going either up or down the stairs, depending on the argument.

“The cat is going up, the tail is used to balance the body of the cat and in this case the tail is elevated upwards so that when the cat uses its rear legs to push up it pushes parallel to the line on which gravity is working on the tail to stabilize itself,” said one commenter.

But at the same time, the Daily Mail quotes another who said cats would raise their tail when going down the stairs to maintain their balance, but not while up.

Is the cat going up or down the stairs?

Our opinion? The cat is clearly going up the stairs. This is how cats go downstairs:

- Megan Willet, additional reporting by Nicky Ryan

Read: This is why people were divided on the colour of *that* dress >

More: Government minister says dress is white and gold, is clearly wrong >