In an interview in the December 16 New Scientist (ungated for now here), psychiatrist Patrick Lemoine explains how what he sells is partly illusion:

How much do doctors use placebo therapy?
The most reliable estimates suggest that around 35 to 40 per cent of all official prescriptions are impure placebos, by which I mean pharmacologically inactive substances contaminated with a tiny amount of active ingredient – not enough to have a clinical effect, but enough for doctors to claim it does. …

Doctors hate not to be able to predict or control the outcome of a treatment, because it makes them feel like charlatans. As a result they tend not to prescribe pure placebos – that is, totally inactive substances – but impure placebos. This way they can fool themselves, at the same time as they fool their patients, that the treatment has predictable, scientifically tested effects.

Can you give an example of an impure placebo?
Magnesium is one. Rare conditions resulting from a deficiency of magnesium produce some symptoms very similar to those of anxiety. Magnesium is therefore often prescribed for anxiety in Europe, even though the cause, in most cases, is unlikely to be magnesium deficiency. …

Are you guilty of prescribing placebos?
Impure placebos, yes. I confess that I prescribe magnesium for anxiety. My patients are generally satisfied and sometimes I even have the impression that not only do they show a remarkable improvement, but their relapse is almost immediate if the treatment is interrupted.

If I’m honest with myself, I don’t really want to know if that improvement is a true pharmacological effect or a placebo effect. On the other hand, I would personally never prescribe homeopathy, because I consider that to be a pure placebo and my conscience wouldn’t allow it. …

Prescribing pure placebos can’t be a good thing, because it involves a lie on the part of the doctor. But if you know what you’re doing, giving an impure placebo can be justified. Even better, though, would be to persuade the patient that chemistry is not always the answer; that there are other ways to heal – through sport, for example, or love.

Doc Lemoin is honest to admit he is selling an illusion, but dishonest to think that this is not a lie if there is any chance whatsoever that a chemical effect is involved.  Don’t expect him to put much effort into pointing out the sport or love alternatives though, or to support allowing non-doctors to sell such illusions.