The Dream Argument
Descartes poses the question whether we can trust our imagination as results from a perception or whether all of our images could be the result of a dream. Descartes' thought experiment reminds us of the following movie.
What are the conclusions? As far as nobody like Morpheus frees us from our common existence, it might be hard to conclude that there is a reality distinct from our imagination. It remains a possibility that everything is a dream, and thus imagination cannot be a foundation for a secure science.
This teaches us the following lesson: It is at least difficult to infer back to an original point of reference from which our images that we in our head originate.
Please, however, keep in mind: this does not say that we have, first, no knowledge, and, second, Descartes also does not say that reality does not exist, he only states that we should suspend our belief and not take beliefs like images as foundational for our sciences.
Further Links: What is a "Metaphysical Realism"? http://plato.stanford.edu/entries/realism-sem-challenge/
I highly recommend the Stanford Encyclopedia as a reliable resource for basic philosophical problems. The article on realism is very helpful: http://plato.stanford.edu/entries/realism/
"In addition, it is misleading to think that there is a straightforward and clear-cut choice between being a realist and a non-realist about a particular subject matter. It is rather the case that one can be more-or-less realist about a particular subject matter. Also, there are many different forms that realism and non-realism can take."Prima facie, these questions might not be so interesting to you, but there are some consequences for our project to develop a critical mindset.

https://www.pinterest.com/pin/322288917055400292/
The costs of misperception can be very high: You choose the wrong leaders, you decide to not vaccinate your children, or you ruin your life because of poor judgement. Media are certainly working on ourselves emotionally. If you learn how to argue, you do not learn for others. You also do not learn for being better than others, but you learn for yourself, in order to avoid mistakes for your own life.
Plato, an ancient philosopher who we will study later this semester, had a similar idea. According to him, we are chained in a cave, and all the truths we see are shadows produced by anonymous people in the background. This idea resembles very much Descartes' idea. For both philosophers the way out of this cave is walked by virtue of reason.

https://i.ytimg.com/vi/ryGPPc5Z5Ng/hqdefault.jpg
The question remains, however, how do we leave this concretely?
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http://i2.kym-cdn.com/photos/images/newsfeed/001/040/017/91d.jpg




