learning - Why does such circuit not work?

Assume I have a lamp and I connect one side to the + pole of one battery, and then the other side to the - pole of another battery (say two batteies of 1.5V). The remaining - and + poles are not connected.

So there is a potential difference between across the lamp, but it does not turn on, why ? It seems to contradict the basic law of electricity.

Note : I am a newbie in electronics/electricty.