Shades of degrees or splitting horses from donkeys? That’s how the debate over the difference between Tennessee whiskey and bourbon usually shakes out. Both share the same set of rules for production, except Tennessee whiskey requires one extra step.

To be a bourbon or a Tennessee whiskey:

• Your recipe, or mash bill, has to be at least 51% corn, rounded out with other grains like rye, wheat and malted barley.

• It cannot be distilled at higher than 160 proof.

• The whiskey must be aged in new, charred-oak barrels.

• The whiskey cannot enter the barrel at higher than 125 proof.

• It cannot be bottled at less than 80 proof.

Now for the differences:

• Bourbon may be made in any state in the USA. Tennessee whiskey must be made in Tennessee. Makes sense.

• Finally, Tennessee whiskey must be filtered through charcoal, called the Lincoln County process, before going into the barrel.

That gets sticky, too. Some distillers think that any whiskey, not just those that follow the rules for bourbon, can be called a Tennessee whiskey as long as it is made in Tennessee.

But historical precedence of makers like Jack Daniel, George Dickel and Charles Nelson made the argument of distinction back in the late 19th century.

Today, it’s state law, but still contested.

That also means, technically, Tennessee whiskey is a bourbon, unless you can argue quantifiably that the charcoal mellowing strips out enough compounds that it is no longer a bourbon, but nobody has done that.

So, the horse trading continues.