Homeopathy (also homœopathy or homoeopathy; from the Greek ὅμοιος, hómoios, "similar" πάθος, páthos, "suffering" or "disease") is a form of alternative medicine first defined by Samuel Hahnemann in the 18th century. Homeopathic practitioners contend that an ill person can be treated using a substance that can produce, in a healthy person, symptoms similar to those of the illness. According to homeopaths, serial dilution, with shaking between each dilution, removes the toxic effects of the remedy while the qualities of the substance are retained by the diluent (water, sugar, or alcohol). The end product is often so diluted that it is indistinguishable from pure water, sugar or alcohol. Practitioners select treatments according to a patient consultation that explores the physical and psychological state of the patient, both of which are considered important to selecting the remedy.