Durgadas explains the subtleties behind the sciences of karma and samsara (reincarnation) as per Hindu and Yogic thought.

Understanding Karma and Reincarnation: 

By Ved Kovid, Durgadas

(c) Ved Kovid Durgadas, All Rights Reserved. 

There is often much talk about karma and reincarnation, but few people understand the deeper view of these sciences in Vedic sects and movements of India. Karma itself is action and Samsara or reincarnation is intimately connected to it and has a deeper science and explanation than simply the terms often floated around in New-Age circles.

In dharmic faiths (Hinduism, Jainism and Buddhism), as in Yoga and Ayurveda as a part of them, one suffers and is reborn as per one's past-life actions (karmas), dictated due to one's food and intake impressions (ahara) that affects one's thinking by vitiating the mind (causing prajnaparadha), leading to adharmika karmas or performing bad actions.

There is no 'sin' in Hinduism, but there are actions done with wisdom (vidya) and without wisdom (avidya), as a consequence of the above. Good actions that give good merits and rewards are known as "punya-karmas", whereas those that give negative results are known as "papa-karmas". 

One is reborn accordingly as per the levels of sattvas (purity ad truth), rajas (agitation and passion) and tamas (darkness and inertia) as per the various samskaras (karmic tendencies) one accrues as per one's actions. These samskaras or vasanas (mental impressions) remain with the astral body at death, being lodged in the silent "mind-stuff" (chitta), the collective mind-consciousness, or if we like, the chitragupta (hidden picture or scribe), that is the chitta. These then come out in the next life, according to the severity.

Ayurvedic and Yogic psychology knows of several levels and layers of the mind according to the astral sheaths:

I. Causal Body Sphere (Karana Sharira)

i. Anandamayakosha: The bliss sheath, the realm of the Karana Chitta or causal mind-stuff and where the Atman or Soul is contained. 

Here in this level of the Chitta is where the samskaras or impressions of various lifetimes and their actions, the collective works (sanchita karma) is stored. It is also from where the prarabda-karma (current karma coming out) is selected from and flows forth into the current incarnation and also where the kriyamana-karmas (the actions we are performing now for the future) are also stored and go into the sanchita for the next lifetime's prarabdha-karma. 

II. Astral Body Sphere (Sukshma Sharira)

ii. Vijnanamayakosha: The wisdom body, the realm of the Buddhi or the intellect and source of mental metabolism and discrimination. This gives us the ability to discriminate between our good and bad actions or not, depending on foods etc. affecting it and past impressions or vasanas.

iii. Manomayakosha: The mental body and the realm of the Manas or emotional mind.Mental impressions shape this level from the physical and emotional plane, including toxic people and conversations etc.

iv. Pranamayakosha: The pranic or breath sheath and the realm of the higher Ahamkara or ego. This is the more astral form above the earth that can be affected by tamasic or lesser influences from negative and higher positive beings and thereby affect the mental sheath and physical mind thereby. 

III. Physical Body Sphere (Sthula Sharira)

v. Annamayakosha: The food or physical sheath and the realm of the Ahankara or ego. The realm of physical matter and also actions.

Each level here also has five subdivisions as per the following:

(i) Sattvas (purity, clarity and perception)

(ii) Sattvas ca rajas (mixed purity / clarity and agitation and passion)

(iii) Rajas (passion and agitation)

(iv) Rajas ca tamas (mixed passion and agitation with dullness and darkness)

(v) Tamas (dullness and darkness)

In Vedanta, rajas and tamas are represented by two broad categories as below:

(i) Vikshepa-shakti, the power of projection, representing rajas. It includes the functions of the mind such as:

-Kshipta (distracted)

-Vikshipta - (imaginative)

These give rise to issues such as moha (delusion), vibhramsa (hallucination), 

chittovega (anxiety), unmada (insanity), bhrama (vertigo) etc.

(ii) Avarana-shakti, the power of veiling and obscuring, representing tamas It includes functions of the mind such as mudha (delusion).

This brings upon issues such as apasmara (epilepsy), sanyasa (comatose state), unmada (insanity, in more extreme forms) etc.

Ayurvedic texts tell us that psychological disorders, diabetes etc. caused by sahajika (congenital) factors, due to being passed on by the ovum or sperm (and missing generations) affects us with diseases that are more complicating (as genetic disorders are), due to the actions we performed in the past and levels of gunas (sattvas, rajas and tamas) we are born into, when our astral bodies, in which the sleepy Soul inhabits, reincarnates as a consequence of it's past actions in the chitta. Thus, while some diseases are caused by diets and lifestyles in this life alone, congenital ones are said to be 'asadhya' (incurable or very difficult to cure), due to the genetic disposition behind them in the familial lineages or bloodline, as also as karmic factors of past lives are behind them!

Ayurveda has two forms of insanity: that cause by external factors as foods, diets, congenital factors, shock, fear and other psychological factors and that caused by seizures of the mind by astral entities. The latter however isn't by random consequence as texts tell us quite emphatically that one is harassed and begins behaving as per a god, demigod, seer, ghost, ghoul or other entity simply as one, in a past-life, have mocked, harassed or committed some crime against them. Karya-karana bhava - the law of cause and effect.

This is how one is reborn as a tree, as an insect or parasite etc. Hindu texts lists dozens of various airborne parasites and bacteria behind diseases and one can be reborn as one of those, or a worm etc. Thus, one is reborn on various levels as per one's past-actions and not otherwise.

Astrology in Hinduism by palmistry, face-reading and one's charts tell us much about their past-life karmas, diseases and periods they will come out, as also their overall makeup and psyche, which also reflects the levels of sattvas, rajas and tamas, as per their mentality in this life-time, to where they're headed in the next lifetime, as per the current samskaras. Of course, one has to make a conscious choice to change these by tapas (austerities) and prayaschitta (atonement) or these will not be changed, transformed or transcended. That is where the greater path of Yoga comes in, but the spiritual Yoga involving homas, devata-pujas, meditations along with mantras and pranayamas to deities etc., not merely exercises (vyayamas) alone!

Thus, the levels and classes of beings is as follows:

I. Sattvika level:

(i) Uttara (highest) - Sattvic portion

Brahmas (those who have knowledge of the four vedas or Brahmins), inventors and those who study dharma or law and order and adhere to it, those who study into the laws of primal nature (physicists etc.)

(ii) Madhyama (middle) - Rajasic portion

Priests who know the Vedas, astrologers and wise ancestors etc.

(iii) Jaganya (lowest) - Tamasic portion

Ascetics, wise seers who recite the Vedas, aeroplane pilots (vaimanikas), astrologers and astronomers and the daitya (strong) classes.

II. Rajasika level:

(i) Uttara (highest) - Sattvic portion

Singers and musicians (heavenly and human), guhyaka (hidden spirits) and yaksha (tree spirits, tree caretakers - botanists and those who take care of wealth of the earth, i.e. extract gemstones, jewelers etc.) classes, chamberlains and good-looking females.

(ii) Madhyama (middle) - Rajasic portion

Kings, royal priests and prime ministers, messengers, lawyers and those engaged in war or military.

(iii) Jaganya (lowest) - Tamasic portion

Killers or murderers, boat-men, rope-dancers, labourers and alcoholics (here would indicate congenital or kulaja alcoholism and addictions).

III. Tamasika level:

(i) Uttara (highest) - Sattvic portion

Musicians and bards, eagles, bragging humans (narcissists, indicating those born with sahaja or congenital psychological issues),rakshasas (violent humans and entities), pishachas (scavenger humans and entities) 

(ii) Madhyama (middle) - Rajasic portion

Elephants horses, labouring classes of humans, those with low intellects, lions, tigers and pigs etc.

(iii) Jaganya (lowest) - Tamasic portion:

Motionless entities (stones, mountain spirits), bacteria, parasites and insects, fish, serpents, tortoises, animals and deer etc.

There are also lesser forms of life, as souls born into anutvas (atoms), paramanus (subatomic particles) and specs of dust also. These are also at the primal level of creation in Hindu creationism, which comes from the spanda-shakti (vibratory power) of the Supreme, first in the form of the subtle tanmatra or shabda (sound), or the primal "Big-Bang", which first produces akasha (ether or space), from which vayu or wind is generated and forms friction into tejas (heat and fire), forming atmosphere or water (antariksha or jala) that solidifies through transmutation into gross matter (prithivi). Each of these is composed of various levels of the paramanus or subatomic particles and that possess varying degrees of the elements within them. This is all explained in the Hindu science of Vaisheshika or atomism and physics, to be studied along with Yoga, Vedanta etc.

References:

Durgadas (Rodney) Lingham, Karma in Yoga and Ayurveda

Vaivasvata Manu, Manu Smriti