LE 3-5-12 General and Logical Deduction

Hey guys, here is first small logical exersize. 

The goal is to distinguish logic as a separate science from other scientific disciplines. We already know that logic deals only with propositions, therms and logical operators, or simply words of language. Logic creates rules of using these words, it does not conduct any physical, or psychological, or any other experiments, in order to gain knowledge, or to discover these rules. Logic works with the language and by the language only.  

So here is an example:

(1)    The ship traveled the distance of 1000 miles, and the time of the travel was 20 hours.

(2)    THEREFORE  the ship traveled with the speed of 50 miles per hour.

As you see, this example has premises and conclusions. The conclusion looks like logical, but its not. The rule that we used to draw this conclusion (computing speed) is set by physical science, not by logic. We still have terms, propositions and logical operators here, but they serve to express physical law, not purely logical.

Another example:

(1)  All metals conduct electricity, and copper is a metal.

(2)  THEREFORE copper conducts electricity.

Here we might think that it is also about physics, but it’s not. The conclusion is made not by the physical rule (even though its completely agrees with physics), its purely logical. Logic sets the rules for the operator “all” , and conclusion was possible because of this rule. If you put wood instead of cupper, and say “ ….., and wood is a metal.”, than the conclusion “THEREFORE wood conducts electricity.” would be still logically  valid, even if it does not agree with the laws of physics.

Exercize: Which example shows logical deduction, and which is deduction of different kind?

1.  The patient had fever, cough and chest pain. It didn’t take long for the doctor to realize, that the patient got infected with flu.

2. When people are happy they are smiling, and tonight I see many smiling faces around. It means that I am surrounded by happy people.

      3.  The computer was working very slow, had a lot of popup windows on the desktop, and gave erratic error messages. IT tech made a conclusion: is was infected with malware.

4. The boss said to paint all walls in this building, it means, that we have to paint this ugly wall in the kitchen too, sense it’s the wall and it’s in this building.

Make up two examples on your own: one is for pure logical deduction, and another is for deduction in general, pick any science or subject that you learned at school, post them in here. Remember that we work in team, so everyone will benefit from your examples, and you will benefit from others.