From the Wikipedia article "Larceny"
Traditionally, a thief must not only gain dominion over the property, but also must move it from its original position. The slightest movement, a hair's breadth, is sufficient. However, the entirety of the property must be moved. As LaFave noted critically this requirement is the difference between rotating a doughnut (larceny) and rotating a pie (not larceny), as all of the doughnut is moved through rotation while the pie's exact center remains in the same place when rotated.
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"It's a handy thing, this experimental attitude," said Castle. "The scientist can be sure of himself before he knows anything. We philosophers should have thought of that."