Patticca Samuppada or dependent arising, the Buddha’s central teaching, is often misunderstood as being about causation (or mistranslated thus, as in the quotation below) but is really about conditionality. Four walls (or at least three) are a condition for having a roof; a roof would be impossible without them. Therefore walls are a condition for the existence of roofs but do not cause them; roofs depend on walls, but are not caused by them.  

Contemplating this principle universally eventually reveals an overview of existence that eradicates the mental poison of spiritual ignorance (avidya), ignorance that is far more than simply not knowing: it is our deep-seated tendency not to want to know about the real nature of things.  

[Ananda:] How deep is this causal law, and how deep it seems! And yet do I regard it as quite plain to understand! 
[The Buddha:] Say not so, Ananda, say not so. Deep is this causal law, and deep it appears to be. It is by not knowing, by not understanding, by not penetrating this doctrine, that this world of men has become entangled like a ball of twine, become covered with mildew, become like munja grass and rushes, and unable to pass beyond the doom of the Waste, the Way of Woe, the Fall, and the Ceaseless Round (of rebirth). 

As Ananda observes, the Buddhist teaching of conditionality is in a way very simple. Yet, as the Buddha insists in reply, its implications are vast beyond imagination. Events and objects arise when the appropriate conditions are present; if certain conditions are present then particular events have the potential to arise, not others. The Buddha summarised the teaching as ‘this being, that becomes’ – in other words, if this phenomenon arises, then that one can arise on the basis of the first. You tend to think that a thing has just one cause, but in fact every object and event you experience is the product of innumerable different conditions, some immediate to the event’s arising, others far away in its historical background. This applies especially to the ideas in your mind at this moment. The factors that have conditioned them are innumerable. You have them not only as a result of reading them, but because of other ideas you have had, and other books you have read too – in fact all the ideas that have ever arisen in your mind have played some part in the evolution of your present set of ideas. Yet all that is just one aspect of the situation. A seemingly infinite number of factors have conditioned the book itself. It has come about partly because I wanted to write it – so there’s a lifetime’s worth of factors peculiar to me – and partly because people are interested in its content. That interest comes from movements in our culture springing from the actions, thoughts and emotions of many generations. Moreover, each one of these has conditions that also go infinitely back in time.  

Meditate on the universality of conditionality. See the conditions that you experience in your own life going further and further back, wider and wider out. Reflect how all of them have affected your particular experience of the present moment. Consider how the present moment also carries all that richness with it, and even now conditions the infinite future.  

According to the Buddha, there are two modes of conditionality, two ways that events can arise. These are represented by the ‘Wheel of Dependent Origination’ and the ‘Spiral of Liberation’ and describe sequences of change that inevitably occur in our being and consciousness – in the first case when you do not try to develop towards Enlightenment, and in the second when you do. The concepts of the Wheel and the Spiral give an overview of the whole process of conditioned existence and its relation to the realm of the Unconditioned.

The Wheel of dependent origination is the closed circle of conditioning factors within which you normally live unless you become aware of your situation and make the attempt to break out of it. Summarising the main conditioning factors, you see that your ignorance of the true nature of things has necessarily led to a particular kind of birth – which has inevitably led, since you have a body with senses and feelings, to the predicament of craving. This tends to produce an addiction to particular ways of behaving, and over a lifetime these habits usually become so entrenched that you never break out of the patterns. The entrenched patterns condition the next life, in which you of course tend to repeat over again. The spiral of liberation moves upward, representing the fact that this predicament can be transcended. Merely because you have feelings, you do not have to react with the craving, hatred and other unskilful emotions that are binding you to the Wheel. You can break out by developing a positive series of conditions – faith in yourself, shamatha, vipashyana, enlightenment – which support one another to produce more and more happy and insightful states of mind. The repetitive nature of the wheel and the unrealised creative potential of the spiral expresses the human situation in a nutshell.

The method of meditation upon conditionality is to dwell upon each of these principal links (nidanas), on both the Wheel and the Spiral, having established a good basis of shamatha. Obviously you need to understand at least roughly what you are doing before you can attempt any useful practice. Ideally, you need to understand the exact meaning of each nidana as well as the relationship between the various nidanas. So it’s likely that considerable thought, further reading and preferably access to people who can help you clarify questions are necessary. This doesn’t mean you cannot engage in the practice until you completely understand, for you could never start if that were really so. Provided there is some basis of prior reflection, the meditation itself will feed back and nourish your intellectual understanding. But for the dharma seed to grow, you’ll need to acknowledge the incompleteness of your understanding.

As usual with vipashyana, begin in a good state of concentration and positive emotion. Ideally, be in the first dhyana. Then turn the concentrated attention upon the opening nidanas of the Spiral, dwelling on each one for a while before moving on to the next. See the table below for the complete sequence of stages of the meditation, which is followed by a brief commentary to aid contemplation at each stage.  
The practice has three phases. In the first you contemplate the seven ‘spiral’ nidanas that describe the whole path of spiritual progress from the point where you make the decision to work with your experience, difficult though that might be, right through to the point where the mind is sufficiently inspired, concentrated and open for insight to arise. In a second phase, contemplation switches to considering the details of how our cyclical, repetitive and unawakened experience depends on a cycle of conditions. The third phase is a contemplation of the process of disenchantment and progressive freedom from that cyclic conditioning process.  

Stages of Contemplation of the Twenty Four Nidanas

MUNDANE ‘SPIRAL’ NIDANAS (Integration towards dhyana) 

In dependence upon dissatisfaction arises faith (sraddha )
In dependence upon faith arises joy (pramodya )
In dependence upon joy arises rapture (priti )
In dependence upon rapture arises calm (prashrabdhi )
In dependence upon calm arises bliss (sukha )
In dependence upon bliss arises concentration (samadhi )

In dependence upon concentration arises knowledge and vision of things as they really are (yathabhutajnanadarshana) 

In dependence upon ignorance (avidya) arise karma-formations (samskaras ) 
In dependence upon karma-formations arises consciousness (vijnana )
In dependence upon consciousness arises the psychophysical organism (namarupa ) 
In dependence upon the psychophysical organism arise the six sense organs (sadayatana ) 
In dependence upon the six sense organs arises contact (sparsha )
In dependence upon contact arises feeling (vedana )
In dependence upon feeling arises craving (trsna )
In dependence upon craving arises attachment (upadana )
In dependence upon attachment arises becoming (bhava )
In dependence upon becoming arises birth (jati )
In dependence upon birth arise old age and death (jara-marana )

CYCLIC NIDANAS (dissolving)
Upon the cessation of birth, old age and death cease
Upon the cessation of becoming, birth ceases
Upon the cessation of attachment, becoming ceases
Upon the cessation of craving, attachment ceases
Upon the cessation of feeling, craving ceases
Upon the cessation of contact, feeling ceases
Upon the cessation of the six sense organs, contact ceases
Upon the cessation of the psychophysical organism, the six sense organs cease 
Upon the cessation of consciousness, the psychophysical organism ceases 
Upon the cessation of karma-formations, consciousness ceases
Upon the cessation of ignorance, karma-formations cease

In dependence upon knowledge and vision of things as they really are arises disenchantment (nirveda ) 
In dependence upon disenchantment arises disentanglement (vairagya )
In dependence upon disentanglement arises freedom (vimukti )
In dependence upon freedom arises knowledge of the destruction of the biases (asravaksayajnana )