Weird consequence of Gauss's law

According to Gauss's Law, the electric field at a surface is the function of only the charge enclosed inside it. But that doesn't make sense. I mean, if I put the surface in an electric field, won't the resultant electric field at the surface change?

• Gauss' law states the total flux through any closed surface is a function of the charge enclosed. If you put your surface in an electric field as many field lines enter it as leave it, so the total flux over the whole surface is zero. You can only have a net flux over the whole surface if there is something within the surface that acts as a source or sink of field lines. – John Rennie Apr 24 '14 at 11:22
• The usual introductory examples make use a carefully chosen symmetries to let you relate the net flux (which Gauss' law talks about) to the field itself (which it does not). This is one origin of student confusion on the matter. – dmckee --- ex-moderator kitten Apr 24 '14 at 15:23