Introduction

Over the years, there have been many attempts at explaining what causes déja experiences. There have also been several attempts at evoking déjà experiences in psychological laboratories and even in the hospital during open-brain surgery (to alleviate intractable epilepsy), but none (up till now) has been successful. It is a highly subjective experience and seems to occur randomly for most people. This makes it very difficult to study. For this reason, the explanations that follow must all be taken with "a grain of salt". You will see that what any particular theorist comes up with depends strongly on which scientific discipline or field he or she belongs to.

As one might imagine, such a baffling and prevalent phenomenon has received considerable critical attention. Theorists, both literary and scientific have come forward with an amazing array of explanations. Interest was particularly intense during the latter half of the previous century, paralleling the rise of psychology, psychiatry, and psychoanalysis as they became scientific disciplines. In France, there were four medical doctoral theses devoted to déjà vu: Bernhard-Leroy (1898), Tobolowska (1900), and Albes (1906), at the University of Paris, and Thibault (1899), at the University of Bordeaux.

Note 1: In most of the following, I shall speak of "déjà vu" for simplicity's sake (until I get to the section on reincarnation where it becomes necessary to distinguish between déjà vécu ("already lived through or experienced") and déjà visité ("already visited or have been to that place").

Note 2:It is quite probable that in speaking about "déjà vu" we are actually talking about a number of experiences which have all been lumped into that term. And it could thus well be the case that each explanation fits one or more forms of déjà experience without explaining all of them.

Note 3: There is quite a bit of overlap between what is presented on this page of explanations and what is available on the history page.

Sigmund Freud once noted (1914), there is a line which divides all explanations of déjà vu into two camps: either one really has experienced something for a second time (one's impression is true) or one has not (the impression is false). (Freud referred to believers and unbelievers.) Thus two categories are created and these can be further subdivided as follows: 

False:

1. Outside influences (e.g., demons) are fooling one
2. One has experienced something very similar
3. The organic apparatus has malfunctioned
4. The psychological mind has played a trick 

True:

1. One has knowledge from a previous lifetime 
2. The universe repeats itself 
3. One has somehow gained access to the future 

In the following we shall take a look at these explanations. The literature is enormous (over 800 books and scientific articles) and to keep this report to a reasonable size, it won't be possible to deal adequately or even mention them all. It is hoped, though, that what is provded here will provide enough information for those interested. If you who is reading this would like to contribute an explanation that is not included in the following, that will be very welcome.