你是人，我也是人，我们都同意这一点。但是说一个人是人类是什么意思呢?

Many people believe that science has already answered this question. They think that it’s been scientifically proven that being human is the same as being a member of the speciesHomo sapiens.It’s true that this is whatsomescientists claim, but others tell a different story. Have a look at the literature on human genetics, evolution, and paleoanthropology, and you’ll find that some scientists equate being human with being a member of genusHomo, others cast the net much wider and include every member of our evolutionary lineage since our common ancestor with the chimpanzee, and still others restrict humanity to the subspeciesHomo sapiens sapiens.

Very strikingly, scientists rarely if ever tell uswhythey choose one or another of these options. In fact, the only way to figure out their views on the matter is to read between the lines of their writings and notice (for example) that some describeHomo erectusas “human” whereas others describe the species as “pre-human.”

The reason for this lack of clarity has got nothing to do with science and everything to do with philosophy. The problem isn’t that there aren’t enough data. There are plenty of data.The problem is that the data are irrelevant. Strange as it may sound, even if scientists knew everything there is to know about our biological lineage, this still wouldn’t settle the question of what it means to be human.

Science excels at discovering, predicting, and explaining facts about the world around us, and it has an ever-expanding arsenal of tools and techniques for accomplishing these things. But not every question concerns matters of fact, and scientific methods are not helpful when trying to answer questions of this sort. It turns out that “What does it mean to be human?” isn’t really a scientific question: it’s a philosophical one. It’s a question about concepts rather than one about facts.

Let me explain….

We make sense of the world by classifying the things around us. We sort them into categories—mental “boxes” if you will. Some categories are scientific ones. Chemical elements, subatomic particles, and biological species are all examples of scientific categories. Mostly, though, we use non-scientific orfolk categories. Folk-categories correspond to our ordinary, everyday ways of classifying things. Categories like “furniture,” “frying pans,” and “days of the week” are crucial for getting along in life, but they don’t play any role in scientific discourse. Furniture, frying pans, and days of the week don’t feature in any scientific laws or theories. Of course, scientists can study frying pans, but they investigate them as lumps of matter (physics) or objects with a certain sort of molecular composition (chemistry). The fact that they are frying pans is strictly irrelevant to science. Their “frying pan-ness” (to coin an awful term) falls out of the picture when we approach them from a scientific angle.

Sometimes, scientific categories correspond to folk categories precisely. Consider the stuff that we call “water.” Anything that’s a bucket of water (a folk category) is also a bucket of H2O (a scientific category), and vice versa. Philosophers express this relation by saying that water isreducibleto H2O, which means that water isthe very same stuffas H2O.

并不是所有的民间分类都可以简化为科学分类。他们中的许多人没有科学上的对应(反之亦然)。想想我们称之为“杂草”的植物种类。对于园丁来说，区分杂草和其他种类的植物是至关重要的，他们之所以能做到这一点，是因为他们已经学会了将某些植物归类为杂草。但“大麻”并不是一个生物类别。它不能被归为任何科学合理的分类类别(杂草没有任何生物学特征将其与其他种类的植物区分开来)。想象一下，有一个来自遥远星系的外星超级植物学家，他知道地球上植物的所有生物学特性——它们的形态、生理、生态、生命周期、进化等等。即使有了这些知识，这位外星植物学家也无法区分杂草和其他植物。To dothat, she would have to learn how Earthlings talk about plants in non-scientific contexts (perhaps by getting some practical lessons in gardening).

“Human” is a folk category, not a scientific one, and science can’t settle the question of what kinds of beings are human for the same reason that it can’t settle the question of what kinds of plants are weeds. Scientists can’t answer these questions because neither of them is a question about facts. When we ask what it means to be human, we’re asking a question about what should be included in a folk category, and when we try to answer it scientifically, we’re trying to match the folk category ‘human’ with a scientific one (for example, ‘genusHomo’), with the unspoken assumption that the former is reducible to the latter.

Once we realize that we are on philosophical rather than scientific terrain, the problem becomes clearer and more tractable. In particular, it becomes easier to question the unspoken assumption that the category of the human is reducible to a scientific category. We can open our minds to the possibility that being human is more like being a weed than it is like being water.

What, then, can philosophy tell us about what it means to be human? Can it deliver the answer that we seek? I’ll tackle this issue in my next blog posting.