 What does ‘unimpeded’ mean? Cicero spoke at 2.99 in terms of there being nothing that presents itself in opposition to the plausibility of the impression. Take the example of the water again. It looks healthy in my glass, it comes from a generally reliable source (my tap), there is nothing to indicate that it is not healthy – nothing, therefore, ‘impeding’, or presenting itself in opposition to, the plausibility of the impression that it is healthy. Say, further, that I then hear on the radio a news report that the water supply in my area has been contaminated. At this point there is something opposing – undercutting, one might say – the plausibility of the impression that the water is healthy and I would not therefore drink it.