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Author | Topic: Induction and Science | |||||||||||||||||||||||
nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
I can do deduction in my head. Oh? You've never read a book on it? You've never opened a math textbook and read Euclid's axioms? Or Russel's? You recreated his entire Principia Mathematica, ex nihilo, starting from a basis of absolutely no training whatsoever? You've never taken notes? Used scratch paper?
Using scratch paper doesn't change the point. Deduction is still abstract. Scratch paper might be used for convenience, but you could replace it with something else (marks in sand, chalkmarks on the road, computer records, etc). It is one of the aspects of deduction, that it is arbitrarily representable. By contrast, measuring temperature requires equipment suitable for that job. We cannot arbitrarily change that the way we can change how we carry out an abstract deduction.
I can't tell the temperature in my head - I need a thermometer to do that. The thermometer is meaningless - literally, the expansion of the mercury indicates nothing - absent the fact that one degree Farenheight has been assumed to have a certain value. Sorry, but you are mistaken about this. I'm not to get into a dualing match about this. Readers can determine for themselves who is right.
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PaulK Member Posts: 17827 Joined: Member Rating: 2.3 |
Any reader literate in English can see that the two questions are different. Moreover in Message 79 you accepted that Newton did use astronomical data. Thus you had already accepted that your question in Message 60 had been answered, and only changed your mind later.
As to your argument you forget the role of terrestrial observations, such as Galileo's experiments with projectiles which increae the number of observations available, Not to mention the fact that there are a considerable number of astronomical observations involved in plotting the orbits of the planets. Newton didn't even need the mass of the planets. He modified Kepler's third law based on gravity and showed that when one mass was very much greater than the other (as the sun's mass is greater than that of the planets) the original is a good approxiation of Kepler's original form. The Cavendish experiment succeeded in providing a measure for the constant G. To claim that it did much more would be to claim that Newton's law of Gravity was accepted for over 100 years without significant empirical support. And you complain loudly about any suggestion that you mean that so obviously you do not beleive that the Cavendish experiment was necessary to Newton. As to this
quote: Firstly this simply does not address the issue. Unless it is your contention that a proposed law is proposed to hold only for the specific observations it is "invented" to explain and there is no expectation that it will be of any use with related data, you are still using induction. Taking induction for granted is very different from not using it at all. Secondly the idea that scientific laws are not descriptions can only hold if we do not assume that there is some underlying reality which the "law" describes. For instance if we were to assume that objects ACTED as if they were mutually attracted by gravitational force, but no such force existed. If there were such a force then Newton's law of Gravity would describe it. However even here you must use induction to confirm that the "invention" will continue to work.e
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crashfrog Member (Idle past 1495 days) Posts: 19762 From: Silver Spring, MD Joined: |
What's point are you trying to make? That you don't do it all in your head. You needed external sources of information to be able to perform this sort of reasoning. Particularly, you needed to be handed the axioms in order to begin deduction. You didn't develop them on your own; you're operating from the axioms that have been accepted by the community of reasoners you wish your deductions to be accepted by.
Deduction is still abstract. A unit of measure is abstract. The idea of a "meter" is abstract; there's no reason that a meter has to be as long as it is, it could easily be longer or shorter. We merely agree to accept without question the length of a meter; it's an axiom that is assumed but not proven. There's no proof that will derive the length of a meter.
We cannot arbitrarily change that the way we can change how we carry out an abstract deduction. Sure we can. We can use an alcohol or mercury thermometer; or take advantage of the differential expansion of metals to create a bimetal strip that changes shape under heat; or we can create an electronic thermometer that measures changes in resistance or capacitance to detect changes in temperature. Temperature is also arbitrarily representable. We can represent and measure temperature in an arbitrary number of ways.
Try throwing away all of your thermometers, and then see if you can still measure temperature. I could do so, inaccurately, with my skin.
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nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
Moreover in Message 79 you accepted that Newton did use astronomical data.
Agreed.
Thus you had already accepted that your question in Message 60 had been answered,
That's a complete fabrication on your part. I agreed that Newton used the data. I never agreed that Newton's law was a generalization of that data.
As to your argument you forget the role of terrestrial observations, such as Galileo's experiments with projectiles which increae the number of observations available, ... These are only evidence of the acceleration due to gravity. They are not evidence supporting an inverse square law.
Not to mention the fact that there are a considerable number of astronomical observations involved in plotting the orbits of the planets.
There were still only 6 planets, and 6 distances from the sun to be used in the supposed induction to an inverse square law. It is my impression that Newton had the law of gravity pretty well worked out on a theoretical basis, and Kepler's laws provided the additional confirmation that led him to announce his law. Newton had been studying circular motion, with the use of his calculus.
Newton didn't even need the mass of the planets. He modified Kepler's third law based on gravity and showed that when one mass was very much greater than the other (as the sun's mass is greater than that of the planets) the original is a good approxiation of Kepler's original form.
Kepler's laws are not a specific case of Newton's law of gravity. There is no easy route from Kepler's laws to the law of gravity. The other direction (deriving Kepler's laws from the law of gravity) isn't trivial either, although it can be done with a knowledge of calculus.
The Cavendish experiment succeeded in providing a measure for the constant G.
Right. And that is what was needed to determine the mass of the earth, sun, planets. Without those masses, the astronomical data could not be used to form specific statements of the form that the law of gravity is said to generalize.
Firstly this simply does not address the issue. Unless it is your contention that a proposed law is proposed to hold only for the specific observations it is "invented" to explain and there is no expectation that it will be of any use with related data, you are still using induction.
I am not understanding this. How is it using induction?
Secondly the idea that scientific laws are not descriptions can only hold if we do not assume that there is some underlying reality which the "law" describes.
Of course I disagree. What did Ohm's law describe, at the time Ohm first proposed it?
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nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
What's point are you trying to make? That you don't do it all in your head. You needed external sources of information to be able to perform this sort of reasoning. Particularly, you needed to be handed the axioms in order to begin deduction.
Getting the axioms is not part of the deduction, either. The deduction does not begin until they are available.
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PaulK Member Posts: 17827 Joined: Member Rating: 2.3 |
More revisionism I'm afraid. Whether you agreed or not about the generalisation your original question was answered - and you accpeted it as an answer (whether you agreed or not).
Galileo's experiments are more relevant than you think since they lead Newton to the idea that under the right conditions a projectile could attain orbit. Which lead to the relationship between gravity and orbits. Remember the whole point is that we are dealing with the same force. Moreover the fact that Galileo found that acceleration was independant of mass indicates that the gravitational force is proportional to the mass of the object - another part of Newton's law. The number of planets does not change the fact that many observations were needed to establish their orbits. Observations made over time (one of the weaknesses of your original example is that it did not even include repeated observatiosn of the same individuals) Your argument about Kepler's laws is mistaken. Newton demonstrated that his law accounted for the same behaviour as Kepler's laws - thus subsuming the evidence and observations supporting Kepler's 3rd law. Later observations confirmed that Newton's version was more correct. As to the final two paragrpahs: 1) If you claim that your proposed law can be used to predict future observations, on what basis can you make that claim ? How can you know that it will apply in cases other those in which it has been directly observed to apply ? My answer is that you are using induction. If you reject induction you still need some reason. So this again comes down to the question you keep avoiding - what is your alternative to induction ? 2) What Ohm's law described when it was proposed is that same as it describes now. If you accept that there is an objective reality out there then this has to be the case. It describes the relationship between the measured quantities of voltage, resistance and current.
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crashfrog Member (Idle past 1495 days) Posts: 19762 From: Silver Spring, MD Joined: |
You're free to redefine "deduction" until you're blue in the face. I'll never understand why anyone would want to have an argument about what words mean. Could any topic be less interesting?
However, getting the external information is not part of the deduction. The deduction does not begin until the data is available. Which exactly proves my point. You can't even begin to deduct until the axioms are supplied; thus, it's not a process you can complete in your head. You can't even begin to deduct absent an external source of information; the same with measurement.
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JustinC Member (Idle past 4872 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
quote:Wouldn't this be quicker if you just showed the deduction? 1. A particular platinum-iridium rod is defined as one meter (not anymore, obviously) 2. My ruler is the same length as the rod 3. My desk is 10 rulers long Ergo, my desk is 10 rulers * (1 rod/1 ruler)*(1 meter/rod)= 10 meters.
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nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
More revisionism I'm afraid. Whether you agreed or not about the generalisation your original question was answered - and you accpeted it as an answer (whether you agreed or not).
That seems dishonest. In the circumstances, I have no interest in further discussion.
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nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
Wouldn't this be quicker if you just showed the deduction?
Your step 2 simply asserts the result of measurement as a premise. Your three steps do not include the actual act of measuring. 1. A particular platinum-iridium rod is defined as one meter (not anymore, obviously) 2. My ruler is the same length as the rod 3. My desk is 10 rulers long Ergo, my desk is 10 rulers * (1 rod/1 ruler)*(1 meter/rod)= 10 meters. Sure, that's a deduction, but the actual act of measuring was not part of that deduction.
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PaulK Member Posts: 17827 Joined: Member Rating: 2.3 |
Yes, your behaviour did seem dishonest.
And it seems more dishonest now. You are using the fact that you were caught falsely accusing me of refusing to answer a question - as an excuse to run away from discussion so you can refuse to answer one of the key questions of this discussion. A question you have to be able to answer for your position to be tenable.
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crashfrog Member (Idle past 1495 days) Posts: 19762 From: Silver Spring, MD Joined: |
Your step 2 simply asserts the result of measurement as a premise. Your three steps do not include the actual act of measuring. It's right there in step two. Comparing the same characteristic of two objects is trivial, but you're making it into something more than it is. Measurement is not the act of putting a ruler next to a desk; it's the act of comparing a known physical trait to an unknown one. That's a deductive process.
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JustinC Member (Idle past 4872 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
I just added that step since it is how most measurement is done (i.e., we don't actually have the standard, just an approximation of it).
Without original step 2: 1. A particular platinum-iridium rod is defined as one meter (not anymore, obviously) 2. My desk is 10 rods long Ergo, my desk is (10 rods)/(1 meter/rod)= 10 meters.
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nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
Comparing the same characteristic of two objects is trivial, ...
Big mistake there, crashfrog. Comparison is a very difficult problem. The reason they use bar codes in the grocery store, is because they haven't solved the problem of doing the comparisons that would be needed to directly recognized the items you are purchasing.
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nwr Member Posts: 6412 From: Geneva, Illinois Joined: Member Rating: 4.5 |
Without original step 2:
But then you appear to be resorting to magic to get to step 2. 1. A particular platinum-iridium rod is defined as one meter (not anymore, obviously) 2. My desk is 10 rods long There seems to be an assumption that measuring is trivial. It isn't.
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