In the Sixth Meditation, Descartes returns to the existence of external objects and the reliability of the senses.
There are several arguments that it is highly likely that there are material bodies in the beginning of the Meditation.
The proof that material bodies exist and that the senses are generally reliable in informing us about them comes in AT 79-80. That is the only viable explanation for the sensory experiences that we, in fact, have.
Nonetheless, the senses are misleading. We naively believe that external objects resemble our sensations. Thus bodies, for instance, are thought to have colors, smells, and tastes in addition to spatial extension. However, extension is all there is to a body: colors, smells, and tastes are added by us.
Therefore, the senses have to be corrected by the intellect if we are to arrive at accurate beliefs.
We finished with a bit from Pierre Bayle’s Dictionary, from the entry on Pyrrho. Bayle claims that Descartes’s position is unstable. If God allows us to be deceived about whether bodies really have colors, why think that God doesn’t deceive us about whether bodies really have extension?