1

PREMISE: （1）Skeptism holds the key to human knowledge, （2）and it believes we cannot know anything to be true 

CONCLUSION: so we should give up searching human knowledge.

ATTACK: the premise and conclusion is controdictory. While the premise says we should pursue human knowledge through a skeptic eye, the conclusion suggest we not pursue it. Skeptism views everything untrue, so knowledge is untrue. Therefore, skeptism cannot help us pursue knowledge.

2

PREMISE: whether smoking marijuana is good or bad is subjective. 

CONCLUSION：So I am right and you are wrong

ATTACK: if smoking marijuana is subjective, then it makes no sense saying the other is wrong. It controdicts with the premise that smoking marijuana is subjective. Nobody can have it both ways.

[I think smoking marijuana is not unethical]

Besides, smoking might not be considered unethical, but it may cause mental and physical heath, which will be influential if the young lay hands on it.