From one of the original letters - the letters are held in The British Library, London.
The full text of Four Articles on the Mahatma Letters to A.P. Sinnett, with detailed page/letter references to the Mahatma Letters to A.P. Sinnett in book form can be found here: pdf link
The Mahatma Letters must be seen against the whole position regarding religion, philosophy and science at the end of the 19th century.
At that time there was a vast religious literature; more important works from India and the East generally but all countries had a religious literature.
There was also a long tradition of Esotericism including the Mysteries, Alchemy, the Kabala and the more practical aspects in Shamanism, Witch Doctors, Yogis, etc.
In a religious field institutions had largely taken over spiritual training and teaching generally according to specific teachers and being based on commonly accepted scriptures.
In the scientific field great strides had been made. In the previous 150 years or so modern science had definitely been born. The scientists of the day considered that, with their present knowledge and rate of progress, they would soon understand all the mysteries of Nature and life. This was in fact an ignorant and an arrogant point of view.
At the time the Letters were written there was a considerable vogue in spiritualism which had started about 40 years previously in America but has spread all over Europe.
Man's thinking was then conditioned by both his religion and science. It was essentially materialistic because of economic conditions tending to make men very selfish.
An overall view of the Letters indicates that the Masters hoped to introduce a scheme of knowledge and spiritual practice to transcend the existing system. Their scheme is essentially acceptable to the intellect. It is based on deep premises concerning the origins of the universe and the law with numerous aspects which 'governs' all natural processes. From these starting premises the whole structure of their teaching can be evolved.
In reading the Letters is has to be borne in mind that they were the first attempt at a formulation of the grand theosophical system. This had been foreshadowed in Isis Unveiled but the main 'framework' had not been established nor had any terminology been agreed on. The terminology was agreed between the Masters and A.P. Sinnett and elaborated and refined by H.P. Blavatsky later on in her writings, particularly The Secret Doctrine.
The teachings as given us in the Masters' Letters foreshadow what was to be considerably expanded later. In many places the material given is very condensed and its meaning obscure but a reading of the Letters after a study of The Secret Doctrine reveals the depth of the teachings.
One of the difficulties the Masters had to encounter was the deep-seated prejudices and preconceptions of the recipients of the Letters. They were conditioned by their particular Christian upbringing which had instilled into them some very firm beliefs, particularly concerning the nature of 'God'. Sinnett was also interested in spiritualism and found it very hard to accept what the Masters had to say about 'spirits' who commonly manifested in seances through mediums.
Another important factor in assessing the worth of the Letters is a proper knowledge of what a Master or an Adept or an Initiate in the sense used in the Letters is. Again at that time the Masters were unable to be specific about their proper occult standing and how their attainment of enlightenment and extraordinary powers was achieved. This can only be understood against a knowledge of the occult constitution of man with its distinction between individuality and personality as so clearly given out by H.P.B. in The Key to Theosophy. To be functioning in consciousness at the individual level (Egoic) is to transcend all the limitations of the ordinary 'personal' man. The liberated Egoic state is one that the ordinary person can hardly envisage. The attainment of this state is the end result of the teaching and training which the Masters give to their accepted pupils. This is dealt with in the last of this series of four talks.
The content of the Letters can be roughly divided into four main sections. Those used by A.T. Barker who published the Letters in September 1893 were:
1) The Occult World Series
2) Philosophical and Theoretical Teachings
3) Probation and Chelaship
4) The Phoenix Venture and the Condition of India
Mr Barker wrote an Introduction to his original edition of the published Letters explaining the circumstances of his taking upon himself the responsibility of making them public.
The Occult World Series refers to a book being written by A.P. Sinnett based on information received in the early letters. The Phoenix Venture refers to an attempt to start an Anglo-Indian newspaper. Both these subjects are of only incidental interest to a modern student.
The Letters on Philosophical and Theoretical teachings and Probation and Chelaship most concern the modern enquirer but the other Letters should be read because they convey much indirect teaching and indicate the Masters' attitude to their correspondents and Western Society in general.
The teachings, whilst against a background of extant religions and philosophical writings all available in the West at that time, were different in much content from them, and were being given out for the first time publicly. A terminology had not yet been agreed and this caused difficulty in giving out the more complicated of this new material. It was difficult for the recipients to comprehend the Masters' meaning. This led to much questioning and even argument.
The new teachings - both destructive of errors and constructive of a genuine, practical Brotherhood ... The Chiefs want a "Brotherhood of Humanity" [ML 6]
The teaching in the letters is scattered throughout them but certain letters do concentrate on specific subjects although not exclusively so. All the Letters have to be read with close attention.
Geoffrey Farthing prepared a table of various topics contained within the letters.
This is contained in the PDF document link
Included in the above PDF document are letter number references to topics related to the After-Death States, and Spiritualism and Spirititual development.
A PDF copy of the Mahatma Letters to A.P. Sinnett is available here:Mahatma Letters PDF
Reproduced from papers for the Spanish Summer School, August 1996