Karl Marx:
It was a historical inevitability.

Niccolo Machiavelli:
So that its subjects will view it with admiration, as a chicken which has the daring and courage to boldly cross the road, but also view it with fear, for whom among them has the strength to contend with such a paragon of avian virtue? In such a manner is the Princely Chicken's dominion maintained.

Hippocrates:
Because of an excess of disagreeable humors in its pancreas

Jacques Derrida:
Any number of contending discourses may be discovered within the act of the chicken crossing the road, and each interpretation is equally valid - as the authorial intent can never be discerned, because structuralism is DEAD, DAMMIT, DEAD!

Thomas de Torquemada:
Give me ten minutes with the heretic, and it will confess.

Timothy Leary:
Because that's the only kind of trip the Establishment would let it take.

Douglas Adams:
Forty-two.

Friedrich Nietzsche:
Because if you gaze too long across the Road, the Road gazes also across you.

Oliver North:
National Security was at stake.

B.F. Skinner:
Because the external influences which pervaded its sensorium from birth had caused it to develop in such a fashion that it would tend to cross roads, even while believing these actions to be of its own free will.

Carl Jung:
The confluence of events in the cultural gestalt necessitated that individual chickens cross roads at this historical juncture, and therefore synchronicitously brought such occurrences into being.

Jean-Paul Sartre:
In order to act in good faith and be true to itself, the chicken found it necessary to cross the road.

Ludwig Wittgenstein:
The possibility of "crossing" was encoded into the objects "chicken" and "road", and circumstances came into being which caused the actualization of this potential occurrence.

Albert Einstein:
Whether the chicken crossed the road or the road crossed the chicken depends upon your frame of reference.

Aristotle:
To actualize its potential.

Buddha:
If you ask this question, you deny your own chicken-nature.

Howard Cosell:
It may very well have been one of the most astonishing events to grace the annals of history. An historic, unprecedented avian biped with the temerity to attempt such an Herculean achievement formerly relegated to Homo Sapiens pedestrians is truly a remarkable occurrence.

Salvador Dali:
The Fish.

Charles Darwin:
It was the logical next step after coming down from the trees.

Emily Dickinson:
Because it could not stop for death.

Epicurus:
For fun.

Ralph Waldo Emerson:
It did not cross the road; it transcended it.

Johann Friedrich von Goethe:
The eternal hen-principle made it do it.

Ernest Hemingway:
To die. In the rain. Alone.

Werner Heisenberg:
We are not sure which side of the road the chicken was on, but it was moving very fast.

David Hume:
Out of custom and habit.

Saddam Hussein:
This was an unprovoked act of rebellion and we were quite justified in dropping 50 tons of nerve gas on it.

Jack Nicholson:
'Cause it (expletive deleted) WANTED to! That's the (expletive deleted) reason!

Pyrrho the Skeptic:
What road?

Ronald Reagan:
I forgot.

John Sununu:
The Air Force was only too happy to provide the transportation, so quite understandably the chicken availed himself of the opportunity.

The Sphinx:
You tell me.

Henry David Thoreau:
To live deliberately... and suck all the marrow out of life.

Mark Twain:
The news of its crossing has been greatly exaggerated. Col. Sanders:
I missed one???