Principles are forever – eternal – and operate at every level. Time invariant and scale invariant; they are not so common. Images and concepts (visualisations) on the other hand are two a penny, and can shift and change as the mood requires. Notice a cat basking in the sun and you become cat. Teacher says the word 'tree' and you become tree. This is the beauty of humans – so impressionable. It all depends on what turns you on.