Would you please help take a look at this LSAT passage:

Only engineering is capable of analyzing the nature of a machine in terms of the successful working of the whole; physics and chemistry determine the material conditions necessary for this success, but cannot express the notion of purpose.

I can't see which does "the notion of purpose" refers to—"the nature of a machine" or "the successful working of the whole"?

As I checked, the meanings of nature the inherent or essential characteristics or constitutions. Still, I found it very different from the meaning of purpose. A purpose, in my view, is not an inherent characteristic or property. So I am confused and would like to seek your help and comment.

I would really appreciate your comments or answers.

2 Answers 2


People build machines for a purpose - to do a job. The "nature of the machine" is the job it was designed to do.

The purpose of a machine is its inherent quality. What it's made of is accidental. You can make a computer with transistors or with tinkertoys. What matters is that it computes.

Suppose you have a machine in front of you and you want to understand it. Perhaps its an artifact of an ancient civilization or found on mars. If you look at it as a physicist or a chemist you can tell which gears move which parts or what chemicals it uses, but you would have to think like an engineer to figure out what its job was.


A purpose is external to a machine as a material object; it something that the designer or the end user has. However, when a machine is being engineered, it necessarily has a purpose, otherwise why would one develop it one way and not some other?

Physics and chemistry provide tools that one can use to their goals, but they do not anyhow express any such goal. You can use them to find out how much fuel you need for an object of a certain mass to reach a certain altitude and velocity, but they do not exactly answer the question, "How do I send a probe to explore the Moon?"

I don't know if you are supposed to know about this, but there is a dichotomy (separation in two and contrasting) in science of positive versus normative. Roughly speaking, positive is about how things are (e.g., physics and chemistry), and normative is about how things should be (e.g., engineering). Of course, once there is a goal ("here is what my machine should do"), there is a criterion of success/failure, something that is not present in physics or chemistry.

So, to answer the question you've stumbled at, "the nature of the machine" seems to mean its behaviour, as determined by the laws of nature (physics, chemistry, etc.), while "the successful working of the whole" — and the word "successful" in particular — reflects the notion of a purpose, a goal that you either achieve or you don't.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .