“Everything is Dual; everything has poles; everything has its pair of opposites; like and unlike are the same; opposites are identical in nature, but different in degree; extremes meet; all truths are but half-truths; all paradoxes may be reconciled.”
This Principle states that things like hot & cold are the same, knowledge & ignorance can be viewed in the same way. Hot and Cold are interconnected with one with an overabundance of energy (Heat) and the other simply lacking that same energy (Cold). Ignorance is lack of knowledge; Darkness lack of light energy and so on. Everything has two sides.