Depending on how thick the wall of the pillar is, I would use a hack saw or something similar that has a thin, fine toothed blade. Cutting it by hand may take longer, but your less likely to damage it. This is where the term 'hast makes waste' deffinetly would apply.

Thanks drose! I was atempting to aviod this one.
Being a sparky I'm better at fixings  things with a scewdriver &/or a ruddy big nudge venier [hammer].
If it has been a lamp it would have been possibly glazed after moulded & kiln fired?
from the post Lori mentioned it has been drilled, obviously after it was produced. Therefore the spiral body may have been weakened in spots, reducing the integral strenght of the pillar?
If it just a solid lump of plaster, the method TimW suggested will work.
However I have a feeling in my water it may be a more delicate operation, from the hesitation of Lori's hubby to grapple tackle it.
The wieght of the wotnot will usualy indicate if is all plaster or something else like concrete on the inside.
Concrete [cement] needs a high speed diamond [tipped] circular saw, that is water cool assisted on the cut. Especialy if it's concrete with blue metal [stone] added.
With tiles they are scored & snapped or knibbled & bogged over later with grouts.
If the thigemebob pillar feels light for it's mass, even though it has what looks like a hole drilled thru, this may have been produced that way & could be like a  green ceramic, which is cured in a mould, then fired when painted & tarted up?
Having experianced a few disasters in my time, if Hubby is unsure, ask a local expert who can view it. You never know they might do it for free for you?