user16: In Buddhist doctrine there is always the problem, that for the sake of understandability, certain concepts are being presented in a solid, substantial way, while actually, one has to keep in the back of one's mind, that by the central tenet of anattā/anātman these concepts are actually not like that. The same applies to kamma/karma, which can be presented as something that a being accumulates and carries with itself in this life and to the next and the ones following.
Now, actually, there is nothing substantial that transmigrates from one life to the next, as is clear from the similes that are used to explain rebirth without soul: a candle that lights another, an echo, a mirror image, the imprint in wax of seal. In these cases, though there is some link between the two sides, nothing actually goes from one to the other (the case with the echo should maybe be reconsidered according to the old Indian theories of sound and the echo). So, what is kamma/karma? How does it stick to the individual?
To take this question one step further, if we admit now that kamma/karma is near-identical with the concept of saṃskāra/saṃkhāra, and therefore with volitions and cetanā, as in this quote from AN 6.63:

cetanāhaṃ bhikkave kammaṃ vadāmi
Intention, I tell you, is kamma

and that by karmic unwholesome action the consciousness "leans towards" unwholesomeness, then how are these leanings supposed to look, how are they thought to be transported from one conscious moment to the next?

user-1: A lot has already been said about the intention part of what kamma is.
I just want to add something on how 'things' get transported to the next mind moment.
If you want to know how that works you really have to dig into the different paccayo's as discribed in the Patthana.
In this case the
Kamma Paccayo.
Important to remember is that there is never just one paccayo at work. There are always several paccayo's working in a moment having impact on the object or the next mind moment or...

user1094: What, precisely, is kamma/karma?
There is no answer to the above question:
Kamma is not in the Oxford Dictionaries. Thus its meaning is dependent on the user.
Karma is defined in the Oxford Dictionary, thus:
Definition of karma in English:
karma
1[mass noun] (in Hinduism and Buddhism) the sum of a person's actions in this and previous states of existence, viewed as deciding their fate in future existences.
Wikipedia defines it as follows:
Karma (Sanskrit: कर्म; IPA: [ˈkərmə] ( listen); Pali: kamma) means action, work or deed;[1] it also refers to the spiritual principle of cause and effect where intent and actions of an individual (cause) influence the future of that individual (effect).[2] Good intent and good deed contribute to good karma and future happiness, while bad intent and bad deed contribute to bad karma and future suffering.[3][4] Karma is closely associated with the idea of rebirth in many schools of Asian religions.[5] In these schools, karma in the present affects one's future in the current life, as well as the nature and quality of future lives - one's saṃsāra.[6]
With origins in ancient India, karma is a key concept in Hinduism, Buddhism, Jainism, Sikhism,[7] and Taoism.[8].
There is no precise definition for Karma.
The word Kamma is not found in the Nikaya Texts of Theravada; however, it is found in compounds. 
A word kammaṃ is found in the Nikaya texts. The words cetanāhaṃ bhikkave kammaṃ vadāmi is an example of usage. The meaning of the word is not understood is clear from the discussion.

user145: There are two main interpretations of how karma is accumulated.
In Sarvastivada branch of philosophy, past actions can be directly related to new consequences, because fundamentally "everything exists" and only the modus of time changes. As things aren't losing the status of existence, they can cause new things. There is a special additional property (called prapti) to relate or un-relate action to the stream of consciousness. So when you perform an action it doesn't need anything else to be able to cause karmical fruit. (Of course it requires other conditions to work.)
In Sautrantika branch of philosophies, actions are accumulated by means of traces (bija-vasanas) in some sort of storehouse consciousness (alaya-vijnana). It works similarly to when you plant the seed of a tree into the ground; the seed disappears but the tree still contains the ability to ripen into certain fruits. Thus, action could be accumulated in something completely different from the action itself. So when you act, you actually change yourself as a whole in a way that accumulates the potential to acquire karmic fruit.
Yes, intention is kamma, but there are two types of kamma (SN 35.145) old kamma and new kamma. Where new kamma is intention (as thinking) and what-is-after-intention (actions of speech and body), while old kamma is your body as whole (i.e. the totality of all organs). In that way you have your old kamma always with yourself in your body (including all organs of perception and intellect).

user18: Karma is not something one accumulates; this question gets asked so often because, as you say, there is a misconception of it being a 'a solid, substantial' entity.
Karma is volition (intention is a bad translation, IMO), or in abhidhamma, the seven javana citta present in an ordinary mind process (i.e. every moment of experience).
All this means is that every experience you have has the potential to affect future experience in some way; the fact that karma produces a result in kind is indicative of how natural the process is - karma is simply the law of causality that moulds our lives according to our actions. That this should continue after death is not a problem for Buddhism since, as I've noted several places here already, death according to Buddhism is just a concept. The mind states continue to arise and cease according to the law of causality.
As to how one mind can affect the next, I really have no answer besides that through the practice of meditation you can verify for yourself that it is indeed the nature of reality; why it is this way is somewhat irrelevant.

16: <p>In Buddhist doctrine there is always the problem, that for the sake of understandability, certain concepts are being presented in a solid, substantial way, while actually, one has to keep in the back of one's mind, that by the central tenet of <em>anattā</em>/<em>anātman</em> these concepts are <strong>actually</strong> not like that. The same applies to <em>kamma</em>/<em>karma</em>, which can be presented as <strong>something</strong> that a being accumulates and carries with itself in this life and to the next and the ones following.</p>

<p>Now, actually, there is nothing substantial that transmigrates from one life to the next, as is clear from the similes that are used to explain rebirth without soul: a candle that lights another, an echo, a mirror image, the imprint in wax of seal. In these cases, though there is some link between the two sides, nothing actually goes from one to the other (the case with the echo should maybe be reconsidered according to the old Indian theories of sound and the echo). So, what is <em>kamma</em>/<em>karma</em>? How does it stick to the individual?</p>

<p>To take this question one step further, if we admit now that <em>kamma</em>/<em>karma</em> is near-identical with the concept of <em>saṃskāra</em>/<em>saṃkhāra</em>, and therefore with volitions and <em>cetanā</em>, as in this quote from <a href="http://www.buddha-vacana.org/sutta/anguttara/06/an06-063.html" rel="nofollow">AN 6.63</a>:</p>

<blockquote>
  <p>cetanāhaṃ bhikkave kammaṃ vadāmi</p>
  
  <p>Intention, I tell you, is kamma</p>
</blockquote>

<p>and that by karmic unwholesome action the consciousness "leans towards" unwholesomeness, then how are these leanings supposed to look, how are they thought to be transported from one conscious moment to the next?</p>
 -1: <p>A lot has already been said about the intention part of what kamma is.</p>

<p>I just want to add something on how 'things' get transported to the next mind moment.
If you want to know how that works you really have to dig into the different paccayo's as discribed in the Patthana.</p>

<p>In this case the
<a href="http://www.wisdomlib.org/buddhism/book/patthana-dhamma/d/doc1843.html" rel="nofollow">Kamma Paccayo</a>.</p>

<p>Important to remember is that there is never just one paccayo at work. There are always several paccayo's working in a moment having impact on the object or the next mind moment or...</p>
 1094: <p><strong>What, precisely, is kamma/karma?</strong></p>

<p>There is no answer to the above question:</p>

<p>Kamma is not in the Oxford Dictionaries. Thus its meaning is dependent on the user.
Karma is defined in the Oxford Dictionary, thus:</p>

<p>Definition of karma in English:</p>

<p>karma</p>

<p>1[mass noun] (in Hinduism and Buddhism) the sum of a person's actions in this and previous states of existence, viewed as deciding their fate in future existences.</p>

<p>Wikipedia defines it as follows:
Karma (Sanskrit: कर्म; IPA: [ˈkərmə] ( listen); Pali: kamma) means action, work or deed;[1] it also refers to the spiritual principle of cause and effect where intent and actions of an individual (cause) influence the future of that individual (effect).[2] Good intent and good deed contribute to good karma and future happiness, while bad intent and bad deed contribute to bad karma and future suffering.[3][4] Karma is closely associated with the idea of rebirth in many schools of Asian religions.[5] In these schools, karma in the present affects one's future in the current life, as well as the nature and quality of future lives - one's saṃsāra.[6]</p>

<p>With origins in ancient India, karma is a key concept in Hinduism, Buddhism, Jainism, Sikhism,[7] and Taoism.[8].</p>

<p><strong>There is no precise definition for Karma.</strong></p>

<p>The word Kamma is not found in the Nikaya Texts of Theravada; however, it is found in compounds. </p>

<p>A word kammaṃ is found in the Nikaya texts. The words <em>cetanāhaṃ bhikkave kammaṃ vadāmi</em> is an example of usage. The meaning of the word is not understood is clear from the discussion.</p>
 145: <p>There are two main interpretations of how <em>karma</em> is accumulated.</p>

<p>In Sarvastivada branch of philosophy, past actions can be directly related to new consequences, because fundamentally "everything exists" and only the modus of time changes. As things aren't losing the status of existence, they can cause new things. There is a special additional property (called <em>prapti</em>) to relate or un-relate action to the stream of consciousness. So when you perform an action it doesn't need anything else to be able to cause karmical fruit. (Of course it requires other conditions to work.)</p>

<p>In Sautrantika branch of philosophies, actions are accumulated by means of traces (<em>bija-vasanas</em>) in some sort of storehouse consciousness (<em>alaya-vijnana</em>). It works similarly to when you plant the seed of a tree into the ground; the seed <em>disappears</em> but the tree still contains the ability to ripen into certain fruits. Thus, action could be accumulated in something completely different from the action itself. So when you act, you actually change yourself as a whole in a way that accumulates the potential to acquire karmic fruit.</p>

<p>Yes, intention is kamma, but there are two types of kamma (<a href="http://www.accesstoinsight.org/tipitaka/sn/sn35/sn35.145.than.html" rel="nofollow">SN 35.145</a>) <em>old kamma</em> and <em>new kamma</em>. Where <em>new kamma</em> is intention (as thinking) and what-is-after-intention (actions of speech and body), while <em>old kamma</em> is your body as whole (i.e. the totality of all organs). In that way you have your <em>old kamma</em> always with yourself in your body (including all organs of perception and intellect).</p>
 18: <p>Karma is not something one accumulates; this question gets asked so often because, as you say, there is a misconception of it being a 'a solid, substantial' entity.</p>

<p>Karma is volition (intention is a bad translation, IMO), or in abhidhamma, the seven <em>javana citta</em> present in an ordinary mind process (i.e. every moment of experience).</p>

<p>All this means is that every experience you have has the potential to affect future experience in some way; the fact that karma produces a result in kind is indicative of how natural the process is - karma is simply the law of causality that moulds our lives according to our actions. That this should continue after death is not a problem for Buddhism since, as I've noted several places here already, death according to Buddhism is just a concept. The mind states continue to arise and cease according to the law of causality.</p>

<p>As to how one mind can affect the next, I really have no answer besides that through the practice of meditation you can verify for yourself that it is indeed the nature of reality; why it is this way is somewhat irrelevant.</p>
