The other day I was using a pair of those stereoscopc glasses that let you see two-dimensional images in three dimensions. I was just wondering what you would see if you could somehow use the glasses to look at an "actual" three-dimensional object with the same colour properties as the paper, wouldn't that theoretically allow you to see four dimensions?

I'm going to say no. Even though we see 3-dimensional objects, the image we see is 2 dimensional. If you take a photograph, it looks 3d (so long as you focus on the same thing the camera did) despite it being 2d.

Technically, no image is 2-dimensional, as if it is nonexistant in one dimension then it can't exist.

Similar to what Rasori stated,

 

Our perception of reality is [usually] limited to three dimensions, and even two dimensional figures and images are still perceived via three-dimensional mechanics (light reflections, refractions, etc).

 

The fourth dimension, which to some is time, is beyond our capacity to perceive and manipulate. We can go ahead a throw a ball through three-dimensional space, but it would be pretty hard to throw that ball through fourth-dimensional time as well. It would seem pretty impossible to throw a ball into the future or back into the past, and thats because it usually is.

All the stereoscopic images do is give you images from two slightly different perspectives, which is imitating what happens when you look at an object — each eye has a slightly different perspective, creating the 3-D image in your mind.

 

The image is static, though. If you took a second set, at a later time, and then another, etc. you'd see in the fourth dimension — you'd have a 3-D movie. Which have been around for decades.