In Plato’s Republic the link between phainesthai and alētheia is of utmost importance. In different passages “truth” is defined by a juxtaposition with a “falsehood” consisting in a deceptive appearance of things. Phainesthai is therefore a characteristic feature of the objects belonging to the lowest level of knowledge. This does not entail, however, that phainesthai should be understood as a mere error or deception. Its meaning is in fact much wider, and not only a negative one. Plato stresses how the whole ascent to the ideas takes place within the phainesthai of the visible. Each step undertaken by the dialektikē technē is related to different ontologic “appearances” of things. The visibility arising from the phainesthai of things is therefore both mimetic (concealing truth) and ontologic (showing that very truth). This paper deals with both these aspects and shows their complementarity in Plato’s polyvalent use of phainesthai.