3rd class, I came across Energy, as a topic in Science, & the first law of thermodynamics, Energy can neither be created, nor destroyed.
Oh, & what a revelation that was. I immediately thought of something else that I was taught (& still believe) can neither be created nor destroyed, Atma (soul).
It felt like I had just discovered a great secret. Atma is energy. (not that all energy is Atma) but Atma is just another form of energy.
Whether it is true or not, I still new to find (& prove, if I want Atma to be officially called, Sambhav's Energy or follow Sambhav's law of Energy) but I have re-found a place to start.