http://www.nationaldayofreason.org/

In the spirit of the day, I emphasize the multiple fallacies I endured reading a "proof" of god.

Logic (Valid)

If A then B (A=B *note - not actually equal like 1=1)

If B then C (B=C)

Therefore If A then C

Logic (Soundness) - the argument makes sense. Note that something can be Logically Valid but not Sound.

If it is sunny, then it is day.

If it is day, then it is cloudy.

Therefore if it is sunny, then it is night. The logic is OK, but the ABC are not actually sound.

Logic (Valid and Sound)

If I vacuum, then there will be loud noise.

If there is noise, then the cat will run to another room.

There if I vacuum, then the cat will run to another room.

Of course, this is pretty simplistic and implies the cat would be further from the vacuum by going to another room, etc.

Fallacy

A=B

C=B

Therefore A=C

NO.

kittens = cute

puppies = cute

kittens = puppies

Wrong. In trying to find the name of this fallacy, I found the following snippet from wiki:

Indeed, there is no logical principle that states:

1. For some x, P(x).

2. For some x, Q(x).

3. Therefore for some x, P(x) and Q(x).

Another way to confuse the logic is to change the definition of a word in the logic to make it seem Sound (see Equivocation).

*shameless stolen from someone... And this one shows both the above:

The sun emits light (Sun implies Light [meaning visible spectrum])

Feathers are light (Feathers implies Light [meaning light weight])

The sun emits feathers