In the words of John Godfrey Saxe (The Six Blind Mean and the Elephant),
"The First approached the Elephant, And happening to fall
Against his broad and sturdy side, At once began to bawl:
God bless me! but the Elephant Is very like a wall!
"The Second, feeling of the tusk, Cried, Ho! what have we here
So very round and smooth and sharp? To me tis mighty clear
This wonder of an Elephant Is very like a spear!"
....
"The Sixth no sooner had begun About the beast to grope,
Than, seizing on the swinging tail That fell within his scope,
I see, quoth he, the Elephant Is very like a rope!
"And so these men of Indostan Disputed loud and long,
Each in his own opinion Exceeding stiff and strong,
Though each was partly in the right, And all were in the wrong!
"So oft in theologic wars, The disputants, I ween,
Rail on in utter ignorance Of what each other mean,
And prate about an Elephant Not one of them has seen!"
I would argue that to an extent the same thing is true of Archeology. Great discoveries have occurred in the last two hundred years, (since, say, Schliemann dug up Troy), but only rarely do the excavators themselves interpret their finds even close to the verdict of the community 50 or 100 years later. Compared to Schliemann's problem though, deciphering Stonehenge is much more difficult - the builders had no writing that we know of, and it was built nearly twice as far into the past.
Dawkins (Richard M., not Clinton R.) believed it was an astronomical observatory. The modern druids think is was a Celtic temple (which is a fantasy; it is much too old for that). Now Johnson thinks it is simple exposition of architecture (sort of, they did it for geometry's sake, and the astronomical alignments are just coincidental - or rather, cherry-picked from a plethora of possible alignments, in the same way that numerology or Bible code does it).
The real truth? IMHO, we're not likely to ever know the real reasons it was built, but the speculation will never end. Far too much disturbance has littered the area with contamination for forensics to be of very much use; any discovery there will be controversial.
