Proof and Evidence

 

 

How do you know when something is true?

 

How do you know whether the sun will rise tomorrow? How do you know that you are not dreaming now? How do you know that your teacher has not been possessed by aliens? And how would you know if he had? In fact, how do you know that anything is true?

Knowing how to tell if something is true is a problem that humans have worried about for thousands of years. It matters in every aspect of what we do. Juries, for example, have to decide whether a defendant is telling the truth when he or she says, "I didn't do it." Scientists have to decide whether new scientific theories are true. Kids have to decide whether Sony is telling the truth when the company claims that PlayStation is better than Nintendo 64.

Some of these claims are easier to prove true (or false) than others. Some very clever people have come up with categories to help us figure out how we know something is true and how certain we can be that it is true. You're going to learn about those categories right now.

 

 

Really knowing something is true: logical proof

 

The best, most convincing kind of argument that something is true is called a logical proof. When something is logically proven, it means that the true answer is the only one that really makes sense. For example, suppose I told you that all Martians are purple and that my friend Quatto is a Martian. What color is Quatto? Of course, you know that Quatto is purple because you know that all Martians are purple. Assuming that the first two statements are right—that all Martians are purple and that Quatto is a Martian—then logically, Quatto has to be purple.

This kind of argument, which is known as deduction, is just about the strongest kind of proof there is that something is true. Unfortunately, most things are really hard to prove true by deduction.

 

 

Assignment #1:

 

There is a very wise robot named Mr. Mind who lives on the Internet. Mr. Mind does not believe that you are human; he thinks you're a robot like him who is only pretending to be human. Go talk to him and prove to him that you are, indeed, human. Then send me an email telling me what you learned from your conversation.

 

 

Making a convincing guess: empirical evidence

 

If you can't logically (or "deductively") prove that something is true, maybe you can put together enough evidence to be convinced that something is probably true. For example, even though I can't logically prove that the sun will rise tomorrow, the fact that it has risen every day of my life convinces me that it probably will do what it has always done in the morning. The fact of the sun rising on past occasions is called my empirical evidence, and I am using inductive reasoning (As opposed to deductive reasoning) to draw the conclusion that the sun will come up again tomorrow. Or to use an example that's closer to home, if two student essays use the exact same words and make the exact same mistakes, I can conclude that one of them probably copied from the other. I can't prove it, though. (By the way, "You can't prove it" won't work with me, so don't even try it.)

It's usually much easier to show that something is probably true using empirical evidence than it is to prove it is true using deductive logic. However, even inductive reasoning has its limits.

 

 

Assignment #2:

 

Pretend that you are an eighth grade Martian and that your teacher has given you a lab to do for homework. He sends you to Earth to study what humans look like, talk like, and act like. He tells you to take a sample of five percent of Earth's population as empirical evidence for your assignment. Imagine that you hop in your school space ship and land on Earth. To be more specific, you land right in the middle of China. Unfortunately, you don't know that you're in China because you flunked Earth geography. In fact, you don't even know what China is.

Write up a lab report that describes how Earth people based on your empirical evidence. By the way, in order to finish your lab report, you also will need to search the Internet to find out or figure out the following facts:

  1. How many people are there on planet Earth?
  2. How many people would make up five percent of the total population of Earth?
  3. How many people are there in China?
  4. If Martian eighth graders came and took five percent of the Earth's population out of China and brought them back to Mars to put in their class aquarium, would there be anybody left in China? And if so, how many people would be left?

When you're done, email your lab report to me as an attachment.

Comments

Name: Edith Jackson
Email address: Slydland@AOL.com
What I liked about this website: I, also, am a middle school science teacher, which for a lot of us is really a disguise for actor, mad scientist, comedian, book worm and hosts of other desriptions. This paper did indeed capture my interest as it would a student and eased the use of the internet for research onto them without the stark threat of possible failure.
What I think could be improved: The story part could be a little less detailed. Students may need to be less engaged with reading the preinstructions as with searching sites on the internet. It depends on how much time you have and of course how disciplined the students are.

Name: Chris Essex
Email address: cessex@indiana.edu
What I liked about this website: Very well written page. Two excellent lessons: I especially like the way the Mr. Mind activity utilizes the Internet in a fun, interactive way.
I think the black on white and the plain Arial/Helvetica font is appropriate for the scientific nature of the page. I like the fact that the assignment headings utilize a different color font than the rest of the text.
What I think could be improved: There is a lot of white space at the top of the page that just cries out for an image that would fit with the topic and the other images on the page. I agree that anchors would be useful on this page. The words that are in a colored font in the middle of a paragraph suggest to me that they are hypertext links but they are not. I would use bold or italic or both but not colored fonts for paragraph text.

Name: Jodi Atkinson
Email address: pjcw@gateway.net
What I liked about this website: This page was wonderful. You put lots of thought into the assignments--I really like Assignment #2 and your directions to students to search the Internet to find out the answers to the questions you asked. I liked the graphics you used, and because of the great colors in the graphics, your white background did work for this page.
What I think could be improved: Only because I don't like to scroll around pages, I suggest that you put some anchors back to the top two sections of the page. Students may need to get back up there to review what you have said about knowing if something is true or logical proof, and it would be helpful to be able to get there without scrolling. Good Job, Michael!

Name: Cathi Grisack
Email address: cathi@cyberhighway.net
What I liked about this website: I love the assignments! Excellent ideas and a really fun page for Science students. Science was never my strong suit, but these activities definitely would have sparked my interest in school. I also think the white background works for your page. It looks "Science-y".
What I think could be improved: Maybe a graphic at the top to spice up the beginning of the page, but overall I really liked it!

Name: Carol Travis
Email address: ctravis@cpsc.k12.in.us
What I liked about this website: I really like the graphics. Good information for a science student.
What I think could be improved: Background color might be helpful, Maybe a different color for each section title, or a graphic at the top.

Name: David Kazansky
Email address: elkkaz@webspan.net
What I liked about this website: This page is a great lesson plan with some good activities. I went to Mr. Mind and attempted to convince it I was human (to no avail). This page sould be a great help to teachers looking for a different way of getting reasoning across to their students.
What I think could be improved: The page itself is good. The only thing I might do is maybe add a couple of site links and add some color to the page.

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