valid vs weak

Every sentence and/or statement we say can be argued against. No matter what the statement is, there is always a way to analyze it. Some arguments sound pretty decent and valid, but in reality, it is considered to be a weak one. They only sound good because it is actually very similar to a valid form of argument.

For example: All fish swim.
Bubbles swims.
So Bubbles is a fish.

Many people would consider that to be a pretty good argument. However, Epstein tells us that it is actually, a weak argument. Sure, Bubbles swims, but so do I! Does that make me a fish? Of course it is true that all fish swim, but the truth is, so do other animals in the sea! Not just animals in the sea though, because there are many other mammals that can swim. Bubbles could be a whale, a dolphin, a dog, even a human! So therefore, that argument is weak. A valid argument, though, would be:

All fish swim.
Bubbles is a fish.
So Bubbles swims.

This here, is a much more accurate statement. If all fish swim, and Bubbles is a fish, then that must mean he swims.