Does water have a memory?

According to modern-day proponents of homeopathy, it must. Homeopathic remedies are made by diluting solutions of various substances so greatly that not even a single molecule of the active substance can be expected to be present in the final medication. Now that even the homeopaths have come to accept this fact, they explain that the water somehow retains the "imprint" or "memory" of the original solute.

In 1985, the late Jacques Benveniste, a French biologist, conducted experiments that purported to show that a certain type of cellular immune response could be brought about by an anti-immunoglobulin agent that had been diluted to such an extent that it is highly unlikely that even one molecule of this agent remained in the aqueous solution.

He interpreted this to indicate that water could somehow retain an impression, or "memory", of a solute that had been diluted out of existence. This result was immediately taken by believers in homeopathy as justification for their dogma that similarly diluted remedies could be effective as alternative medical agents.

The consensus among chemists is that any temporary disruption of the water structure by a dissolved agent would disappear within a fraction of a second after its removal by dilution, owing to the vigorous thermal motions of the water molecules. Benveniste's results have never been convincingly replicated by other scientists.