One of the key concepts that underpin the interaction between natural products and receptors is the principle of causality that was explained by Kant. In the case of receptors, they can control both a local (granular) and a physiological (systemic) effect. It is not always necessary to understand the details of all the steps that lie between these since knowledge of molecular binding and physiological endpoint and the substantive nature of the relationship between them may enable manipulation and control. One of the most common classes of receptors are G Protein Coupled Receptors (GPCRs). Taste, odour and vision receptors are examples of GPCRs. Taste receptors seem to have a significant extra-oral function and are involved in more than simply taste transduction. In terms of physiological effect, enzyme inhibitors are an important class of medicinal compounds. Studies of antimicrobial resistance (AMR) suggests that targeting multiple enzymes associated with a particular microbial physiological function (for example cell wall construction or energy metabolism) may facilitate overcoming AMR. This may be important as increasing numbers of disease states (including, for example, Alzheimer’s Disease) may be exacerbated by inflammation which is provoked by infection.