The conditioned body and mind are nothing more (and nothing less) than an ever changing bundle of kamma which at any given moment is the result of previous volitional fabrications (i.e. kamma) consisting of bodily actions, speech, thoughts and emotions, etc.. The current condition of this bundle of kamma-in-flux is largely dependent upon these previous activities of body, speech, and mind. That said, it's important to understand that not every specific thing that happens to this conditioned body and mind is a direct result of our past actions in a strictly deterministic sense. The conditioned body and mind can also be affected by naturally occurring kamma of the environment such as natural disasters like tsunami and earthquakes, etc.. Even though it's accurate to say that the natural environment that we're born into is dependent upon our previous kamma, once the body/mind is born into a conditioned environment things can occur which are no fault of that particular bundle of aggregates, over and above being born into that particular world where natural disasters can arise.
Truly, the Buddhist understanding of kamma is very profound and difficult to fathom completely, as it's directly related to one of the greatest discoveries of human history, the discovery of dependent origination. But of this much we can be certain: skillful (kusala), productive actions of body, speech, and mind are causes of happiness, and unskillful (akusala), unproductive actions of body, speech, and mind are causes of suffering. This can be experientially verified by anyone willing to clearly investigate the results of their own actions.
And so the question arises as to what exactly are the unskillful actions of body, speech and mind which cause suffering, and should therefore be abandoned? This can be the basis of quite a thorough analysis of fabrications (sankhara), but here we can focus on the general formula of dependent origination, so as to identify the causes of suffering. First of all, let's see how the Buddha states his twelvefold version. In the Bodhi Sutta (Ud 1.3) the Buddha describes the twelvefold dependent origination that he discerned during the first watch on the night of his enlightenment:
From ignorance as a requisite condition come fabrications.
From fabrications as a requisite condition comes consciousness.
From consciousness as a requisite condition comes name-and-form.
From name-and-form as a requisite condition come the six sense media.
From the six sense media as a requisite condition comes contact.
From contact as a requisite condition comes feeling.
From feeling as a requisite condition comes craving.
From craving as a requisite condition comes clinging/sustenance [grasping].
From clinging/sustenance as a requisite condition comes becoming.
From becoming as a requisite condition comes birth.
From birth as a requisite condition, then old age and death, sorrow, lamentation, pain, distress, and despair come into play. Such is the origination of this entire mass of stress and suffering.
Of these twelve factors, five are causes of suffering: ignorance, fabrications, craving, grasping, and becoming. The remaining seven are the effects of suffering resulting from these five causes. So right here we have not only the causes of suffering, the second noble truth, but also the resultant suffering that is the first noble truth.
These twelve factors can be seen as operating over three lifetimes, where ignorance and fabrications correspond to the past life, consciousness refers to the rebirth consciousness of this present life, which then includes everything up to and including becoming, and the eleventh and twelfth links of birth and death refer to the next life after this one. These twelve factors can also be seen as operational in the present life, and indeed in any moment conditioned by ignorance. In order to get a better idea of how these twelve links operate in the present, we can superimpose the eighteen elements over these twelve nidanas as follows:
Of the five causal factors mentioned above, craving is singled out as the cause of suffering, and ignorance is singled out as being the cause of craving. So it seems appropriate to focus our attention on these two phenomena as the pathway leading to the cessation of suffering. Ignorance (avijja), generally speaking, refers to ignorance of the four noble truths, and specifically, it refers to ignorantly identifying with conditioned phenomena as being a self or the possessions of a self. It's what gives rise to all fabrications of a 'self' experiencing a 'world.' This ignorant identification can be brought to cessation through correct discernment: the discernment of impermanence, suffering, not-self, and dependent origination, all of which are aspects of the contemplation of emptiness. So we can see that contemplating emptiness is a meta-practice for discernment, as it involves all of these insights, and is therefore a complete contemplation for bringing ignorance to cessation.
Craving (tanha) refers to the sixfold sensory craving and aversion arising as a result of identifying with the pleasant and unpleasant sixfold sensory feelings of the feeling aggregate, which are dependently produced through sixfold sensory contact as outlined above. Craving is also brought to cessation through the cessation of ignorant identification by the above mentioned discernment, but can also be effectively worked on by the path factors of ethical conduct (sila) and meditative stabilization (jhana), especially meditation themes which give rise to dispassion (viraga). Ethical conduct gives one the precepts to use as a frame of reference to avoid unskillful craving, while meditative stability of mind allows the mind to calm down and settle into a pleasant, dispassionate abiding, thereby not being inclined to seek out objects of sensory craving. Thus, the three path aggregations of ethical conduct, meditation, and discernment can and should be integrated so as to be the most effective means to bring suffering to cessation.
And so the craving (and aversion) arising from ignorantly identifying with conditioned phenomena, and the inevitable suffering that results from such identification and craving, constitutes the truth of the origin of suffering. We can diagram these key links in the twelvefold chain of dependent origination as follows:
And the purpose of the path is to see these conditioned phenomena for what they are: impermanent, unsatisfactory (prone to suffering), and not-self.