Analogously, in medicine, many different pathogens can cause the same symptoms (_e.g._, sneezing, or fever), but doctors care about distinguishing different illnesses by etiology, not just symptoms, because distinct physical mechanisms can give rise to distinct treatment decisions, if not immediately, then at least in principle. For example, a bacterial illness will respond to antibiotics, but a viral one won't—or today's treatments might be equally effective against two different species of bacteria, but future drugs might work better on one or the other.
Analogously, in medicine, many different pathogens can cause the same symptoms (_e.g._, sneezing, or fever), but doctors care about distinguishing different illnesses by etiology, not just symptoms, because distinct physical mechanisms can give rise to distinct treatment decisions, if not immediately, then at least in principle. For example, a bacterial illness will respond to antibiotics, but a viral one won't—or today's treatments might be equally effective against two different species of bacteria, but future drugs might work better on one or the other.