The claims made in that one sentence are: (a) All that up to…
The claims made in that one sentence are: (a) All that up to the present time I have accepted as most true and certain I have learned either from the senses or through the senses; (b) It is sometimes proved to me that these senses are deceptive; and (c) It is wiser not to trust entirely to anything by which we have once been deceived. The conclusion of the argument made in this paragraph is left unstated. It is something like: the senses should not be trusted. Two of the three statements work together to support this conclusion. Which two?