All things exist on a spectrum between two opposites.
Thesis and antithesis are identical in nature but different in degree.
This means that opposites are indeed the same thing just different expressions of the same "vibration"
References
The KybalionThe Kybalion
By Three Initiates
(likely *William W. Atikinson so sayeth wikipedia (although he does seem a likely candidate judging from his other book "The Four Arcane Truths"))