If a tree falls in a forest and no one is around to hear it, does it make a sound? Well, you may need to ask a philosopher or a physicist if you have a free afternoon (and evening) to hear the answer(s). More important is the force that caused the tree to fall in the first place. Did it succumb to structural deficiencies and crumble like a bad NFL team's defense in the fourth quarter? Or did it succumb to destabilizing root rot? It may not seem like this issue would matter in a forest where there is no one to hear a tree fall; but what if no one was there to hear the tree fall merely because no one was home at the time? What if the tree actually fell on a home, or a parked car, or the neighbors' (mostly) innocent goat? Sure, the goat might have heard noises, but really, who cares? It was a goat. Pass the mint jelly. We still need to know why the tree fell. In fact, it would have been better to know that the tree was at risk of falling before it actually fell, so that the car could have been parked somewhere else, or the goat could have been penned in another field, or the house could have been...well, protected by any pruning necessary to make the tree safe. Or alternatively, there's always euthanasia (called firewood in PG-13 households).
This is where an arborist comes in. Arborists are horticulturists who specialize in the care of trees. They identify problems with health, stability, and structural integrity, and prescribe necessary procedures to correct these problems in order to keep homes, parked cars, and even goats safe. They are the most familiar type of horticulturists because they work with the most prominent plants in the garden; namely, trees. Unlike arborists, most of your other horticulturists are placed in virtually no danger at all. Those lads and lasses who work in nurseries, for example, don't really have to worry about a tulip falling over and crushing them, or getting their hand chopped off in a water pitcher.
Like many of the weird varieties of trees they assess, arborists are an odd breed. They love trees way too much to work in other, more lucrative industries. Unfortunately, money does not grow on trees. The reward for a career in arboriculture, the horticulture of trees, comes from being able to do what one loves to do. Those who do not enjoy doing it should probably do something else; hopefully something fulfilling and lucrative.