However, one can also cognize the existence of the thing prior to the perception of it, and therefore cognize it comparatively a priori, if only it i… - Immanuel Kant

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However, one can also cognize the existence of the thing prior to the perception of it, and therefore cognize it comparatively a priori, if only it is connected with some perceptions in accordance with the principles of their empirical connection (the analogies). For in that case the existence of the thing is still connected with our perceptions in a possible experience, and with the guidance of the analogies we can get from our actual perceptions to the thing in the series of possible perceptions. Thus we cognize the existence of a magnetic matter penetrating all bodies from the perception of attracted iron filings, although an immediate perception of this matter is impossible for us given the construction of our organs. For in accordance with the laws of sensibility and the context of our perceptions we could also happen upon the immediate empirical intuition of it in an experience of if our senses, the crudeness of which does not affect the form of possible experience in general, were finer. Thus wherever perception and whatever is appended to it in accordance with empirical laws reaches, there too reaches our cognition of the existence of things. If we do not being with experience, or proceed in accordance with laws of the empirical connection of appearances, then we are only making a vain display of wanting to discover or research the existence of any thing.