The most popular legend behind Lord Shiva’s third eye goes like this –

Once, while Shiva sat rapt in meditation, his consort, Parvati, came up from behind and in a moment of zest, playfully closed both his eyes with the palms of her hands. Soon as she had done so, the whole world was plunged into darkness and ominous turmoil. To prevent the impending catastrophe, there immediately sprung from Shiva’s forehead a fiery third eye, and thus the world was saved from the inevitable disaster which would have followed.

The fierce light from his third eye is so powerful and destructive, that since then, he only opens it to destroy all that is unconscious, dark, and dualistic in this universe. Shiva’s third eye opens to end all illusion!

I heard someone give a pseudo scientific explanation to Shiva’s third eye. He claimed that Shiva may have been a living person long in the past, a baby born to some powerful and respected leader of a tribe, but with a rare genetic deformity that gave him a third eye. Back in those days, there was no knowledge of genetics and so the tribals must have looked at it as a miracle and elevated Shiva’s status to that of God.

This sort of reasoning comes from choosing to look at just one aspect, applying some idea, and trying to come up with a quick and dirty explanation, conveniently ignoring everything that it conflicts with.

What I understand from the legend is that, the concept of Shiva’s third eye also known as the inner eye may actually refer to the mind’s eye or the eye of wisdom or knowledge. The fact that its situated on the forehead may not be without a reason. I’ve realized that the mind’s eye exactly fits the description of Shiva’s third eye and for humans is the best and the only proper way to understand reality.