Elements Of Physics, Or, Natural Philosophy, General And Medical, Volume Ii Book

Regarding Epicurean's point of view should we make decisions based on reasoning or not. It's a bit confusing for me. Example: You see a mirage, based on their point of view what we are seeing is true due to physics and we are seeing the refraction of light from the sky by heated air. But, our reasoning based on that, that there is water there, is wrong. In sum, they don't call it an illusion, they believe what we see is true, we just should not make any opinion based on that. But, they also believe we should not go toward the mirage ,so to me, it's still using logics and reasoning, I don't quite get it what they mean by not making decisions based on what we see ? .......