It is perhaps not without interest to turn into a by-path at this point of our road.  All the illustrations which we have picked out so far have referred to strictly economic conditions.  But we ought not to forget that these economic problems of commerce and industry are everywhere in contact with legal interests as well.  In order to indicate the manifoldness of problems accessible to the experimental method, we may discuss our last question, the question of packing and of labels, in this legal relation too.  All the packings, covers, labels, trademarks, and names by which the manufacturer tries to stimulate the attention, the imagination, and the suggestibility of the customer may easily draw a large part of their psychological effectiveness from without, as soon as they imitate the appearance of articles which are well introduced and favored in the market.  If the public is familiar with and favorably inclined toward an article on account of its inner values or on account of its being much advertised, a similar name or a similar packing may offer efficient help to a rival article.  The law of course protects the label and the deceiving imitation can be prosecuted.  But no law can determine by general conceptions the exact point at which the similarity becomes legally unallowable.  This creates a situation which has given rise to endless difficulties in practical life.

If everything were forbidden which by its similarity to an accredited article might lead to a possible confusion in the mind of the quite careless and inattentive customer, any article once in the market would have a monopoly in its line.  As soon as a typewriter or an automobile or a pencil or a mineral water existed, no second kind could have access to the market, as with a high degree of carelessness one economic rival may be taken for another, even if the new typewriter or the new pencil has a new form and color and name.  On the other side, the purchaser could never have a feeling of security if imitations were considered as still legally justifiable when the difference is so small that it needs an intense mental effort and careful examination of details to notice it.

The result is that the jurisdiction fluctuates between these two extremes in a most alarming way, and this seems to hold true in all countries.  In theory:  “There is substantial agreement that infringement occurs when the marks, names, labels, or packings of one trader resemble those of another sufficiently to make it probable that ordinary purchasers, exercising no more care than such persons usually do in purchasing the article in question, will be deceived.”  But it depends upon the trade experts and the judges to give meaning to such a statement in the particular case, as the amount of care which purchasers usually exercise can be understood very differently.  Sometimes the customer is expected to proceed with an attention which is most subtly adjusted to the finest differences, and sometimes it is taken for