All apparitions of the Virgin Mary are classified by the Roman Catholic Church as private revelations. Joseph, Cardinal Ratzinger, when Prefect of the Congregation for the Doctrine of the Faith wrote in 'The message of Fatima, 2000': "The teaching of the Church distinguishes between 'public revelation' and 'private revelations'. The two realities differ not only in degree but also in essence"... "In this context, it now becomes possible to understand rightly the concept of private revelation, which refers to all the visions and revelations which have taken place since the completion of the New Testament. This is the category to which we must assign the message of Fatima. In this respect, let us listen once again to the Catechism of the Catholic Church: Throughout the ages, there have been so-called 'private' revelations, some of which have been recognized by the authority of the Church... It is not their role to complete Christ's definitive Revelation, but to help live more fully by it in a certain period of history" (No. 67). The Catholic Church teaches that public revelation was completed, and therefore was concluded, with the death of the last apostle (Vatican II, Dei Verbum 4), but private revelation has continued. The church holds that approved private revelations, such as visions, voices and apparitions have been judged as coming from God in all probability, but they do not have to be accepted by the faithful whereas teachings within the deposit of faith do have to be believed and accepted. That said, these apparitions of the Virgin Mary, especially the two major ones of Lourdes and Fatima, have assumed an importance equal to biblical revelations and the Gospels themselves. However Marian apparitions really are in the realm of private revelations and thus do not have to be believed as having supernatural origins. This study sets out to show that Marian apparitions actually have their origins in natural not supernatural phenomena.Whilst there have been hundreds, perhaps thousands of Marian apparitions only 16 have been classified as 'Bishop Approved Apparitions with Vatican Recognition' and 7 ' Coptic Approved Apparitions'. This book refers to several of these.Most often, Marian apparitions occur in Roman Catholic countries wherein the seers are usually young children between the ages of 6 and 12. One natural explanation of Marian apparitions was suggested by the American parapsychologist D. Scott Rogo wrote that it is "possible that they are projections of images latent in our minds which literally become temporarily real on rare occasions.....The key to understanding Marian apparitions may be in their tendency to occur at times of social and/or political crisis. At such times of stress, some form of mass telepathic communication may occur in the collective unconscious of the threatened culture. This may lead to the formation of a "group mind", which, in turn, results in the projection of a Marian visitation." Quite how that would result in apparitions such as Lourdes and Fatima is not clear. What were the means?Ruling out the supernatural, here, the author examines natural causes beginning with hallucinations such as: the religious ones hierophany associated with sacred groves; apophenia, seeing patterns within random data and pareidolia when random stimuli, images or sounds are transformed by our minds into familiar patterns where none actually exists. Biological and geological causes are examined such as: marsh gases seepages of abiotic or natural gases causing hallucinations; geomagnetic and natural electrical discharges such as thunderstorms and especially White Ladies, dazzling balls of light.Other possible causes may arise out of the psychological traits of pre-pubescent girls and especially the levels of magnetite in their brains. One of the characteristics of the alleged Marian utterances is the variability of their reading difficulties levels as measured on the Gunning Fog Index.