user14468: What prevents us from attaining Nibbana?
Is it the ignorance or the craving?
So, what should we focus on, in order to attain Nibbana?
Is it uprooting the craving or uprooting the ignorance?
Because of what reason the uprooting of craving happen?
and
Because of what reason the uprooting of ignorance happen?

user13694: Ignorance is the root which conditions the mind, distorting our perception, thoughts and views.
We ignore the emptiness of the khandhas, and assign a permanent, fixed self to "our" actions, thoughts and words. The ignorant mind creates the idea of a doer, a perceiver, a knower, which is independent and in control of the khandhas. We see the world as something which can be controlled and possessed by that self.
We ignore the impermanence of conditioned phenomena, and we cling to things, feelings and events, wrongly assuming that they will last forever.
We ignore that happiness and suffering do not come from outside, but it is the mind which creates the internal conditions for those states, according to its past habits and tendencies, and to its past kamma. We ignore the fact that all conditioned phenomena are unsatisfactory at last, and that, because of their impermanence, the satisfaction they bring will eventually come to an end.
We ignore that there is a escape to suffering, and a alternative a unstable, conditioned happiness. We ignore the possibility of Nibbana.
We ignore, in sum, our ignorance, which perpetuates the wandering through life.
The mind does not know these things, and as a result, it grasps the world from a illusory perspective, not seeing things as they are.
Ignorance (not merely intellectual, but also experiential, internalized) is the spark which ignites the flame of craving and aversion.
Understanding the roots and causes of suffering, you eradicate both, the seeds of ignorance and craving.
Kind regards!

user43: First of all, "what prevents us" is not understanding what the Nirvana actually is, in real life. Specifically, not understanding that Nirvana is tathata, not knowing what tathata is, not knowing how tathata is violated, and therefore not understanding how tathata can be restored -- and so completely not understanding the Four Noble Truths and the Eightfold Noble Path.
When none of this is understood, it can't be practiced.
Second problem, is endless procrastination, or "feeding on wrong food types". Because we're used to getting our entertainment, our information, our distraction from depression, and our mental energy, from all kinds of dirty worldly sources - like social networks,  TV series, or even talking about "dharma" (repeating the concepts without actually understanding the underlying meaning) - we habitually keep going to these sources moment after moment, instead of stopping to see reality. We keep feeding, and this keeps the cycle spinning, it creates inertia that pushes us forward.
The only way to achieve any change is to

Stop repeating the concepts and try to understand the deeper meaning
Understand tathata
Actually understand Four Noble Truths
Stop procrastinating and feeding on wrong food types
Stop breaking tathata and start changing our life to move towards tathata


user-1: Upasaka Damith,
What prevents us from attaining Nibbana?
Is it the ignorance or the craving?
Not knowing is the cause of craving, craving effects improper attention, cause not knowing to 'resist'... or as other already mentioned, it's a matter of "co-arising".
So, what should we focus on, in order to attain Nibbana?
To put it in other words: "What's the right effort?"
To uphold right view, doing merits (10 kinds of them) and try to keep proper attention alive. 

"One tries to abandon wrong view & to enter into right view: This is one's right effort...
"One tries to abandon wrong resolve & to enter into right resolve: This is one's right effort...
"One tries to abandon wrong speech & to enter into right speech: This is one's right effort...
"One tries to abandon wrong action & to enter into right action: This is one's right effort...
"One tries to abandon wrong livelihood & to enter into right livelihood: This is one's right effort."
— MN 117

Once right view is firm, the maintaining of proper attention (attention of what gives birth of phenomenas) is most importand to carry on.
Is it uprooting the craving or uprooting the ignorance?
When not-knowing is totally uprooted, craving has no more cause.
Because of what reason the uprooting of craving happen?
and
Because of what reason the uprooting of ignorance happen?
By the forth Noble truth, putting this very Noble Eightfold path into practice, follow it, not-knowing and craving finds it's end.
(Note that this is not given for trade, stacks, exchange or entertainment but to leave the bonds to this world)

user254: It's a "false dichotomy" to ask, "Is it this or that?" -- because it's both: they're related.
Given the "three poisons" (ignorance, desire, and aversion) I think that ignorance is described as the "root" of the other two -- it's because of ignorance that there's desire.
The word "ignorance" has a range of meanings: What is the difference between moha (delusion) and avijja (ignorance)?
I think that the four noble truths talk about the cessation of craving; and that the doctrine of the twelve nidanas say that craving is conditioned by sensation -- that it's caused or fuelled by e.g. "delighting" in pleasant sensations, aversion to unpleasant sensations, ignorance during neutral sensations.
So instead there should be "just seeing" and so on.
Another (more complicated) answer is that it's caused by habits or habitual tendencies, different kinds of desires and ignorance and wrong views: see for example What is effluent?
--
A more literal answer, I read that the 12 nidanas can be divided into groups:

Causal process of previous life:


Ignorance
Sankharas

Process of effect in the present life:


Consciousness
Name-and-form
Six sense-bases
Contact
Feeling/sensation

Causal process in the present life


Greed
Appropriation
Becoming

Process of effect of future life:


Birth
Death


According to that model it's the link between 7 and 8 which you can affect, i.e. that where it's possible to "stop the wheel" -- because that's the part of it which happens in the present.

14468: <p>What prevents us from attaining Nibbana?<br>
Is it the <strong>ignorance</strong> or the <strong>craving</strong>?</p>

<p>So, what should we focus on, in order to attain Nibbana?<br>
Is it <strong>uprooting the craving</strong> or <strong>uprooting the ignorance</strong>?</p>

<p>Because of what reason the <strong>uprooting of craving</strong> happen?<br>
and<br>
Because of what reason the <strong>uprooting of ignorance</strong> happen?</p>
 13694: <p>Ignorance is the root which conditions the mind, distorting our perception, thoughts and views.</p>

<p>We ignore the emptiness of the khandhas, and assign a permanent, fixed self to "our" actions, thoughts and words. The ignorant mind creates the idea of a doer, a perceiver, a knower, which is independent and in control of the khandhas. We see the world as something which can be controlled and possessed by that self.</p>

<p>We ignore the impermanence of conditioned phenomena, and we cling to things, feelings and events, wrongly assuming that they will last forever.</p>

<p>We ignore that happiness and suffering do not come from outside, but it is the mind which creates the internal conditions for those states, according to its past habits and tendencies, and to its past kamma. We ignore the fact that all conditioned phenomena are unsatisfactory at last, and that, because of their impermanence, the satisfaction they bring will eventually come to an end.</p>

<p>We ignore that there is a escape to suffering, and a alternative a unstable, conditioned happiness. We ignore the possibility of Nibbana.</p>

<p>We ignore, in sum, our ignorance, which perpetuates the wandering through life.</p>

<p>The mind does not know these things, and as a result, it grasps the world from a illusory perspective, not seeing things as they are.</p>

<p>Ignorance (not merely intellectual, but also experiential, internalized) is the spark which ignites the flame of craving and aversion.</p>

<p>Understanding the roots and causes of suffering, you eradicate both, the seeds of ignorance and craving.</p>

<p>Kind regards!</p>
 43: <p>First of all, "what prevents us" is not understanding what the Nirvana actually is, in real life. Specifically, not understanding that Nirvana is <em>tathata</em>, not knowing what <em>tathata</em> is, not knowing how <em>tathata</em> is violated, and therefore not understanding how <em>tathata</em> can be restored -- and so completely not understanding the Four Noble Truths and the Eightfold Noble Path.</p>

<p>When none of this is understood, it can't be practiced.</p>

<p>Second problem, is endless procrastination, or "feeding on wrong food types". Because we're used to getting our entertainment, our information, our distraction from depression, and our mental energy, from all kinds of dirty worldly sources - like social networks,  TV series, or even talking about "dharma" (repeating the concepts without actually understanding the underlying meaning) - we habitually keep going to these sources moment after moment, instead of stopping to see reality. We keep feeding, and this keeps the cycle spinning, it creates inertia that pushes us forward.</p>

<p>The only way to achieve any change is to</p>

<ol>
<li>Stop repeating the concepts and try to understand the deeper meaning</li>
<li>Understand <em>tathata</em></li>
<li>Actually understand Four Noble Truths</li>
<li>Stop procrastinating and feeding on wrong food types</li>
<li>Stop breaking <em>tathata</em> and start changing our life to move towards <em>tathata</em></li>
</ol>
 -1: <p>Upasaka Damith,</p>

<p><code>What prevents us from attaining Nibbana?
Is it the ignorance or the craving?</code></p>

<p>Not knowing is the cause of craving, craving effects improper attention, cause not knowing to 'resist'... or as other already mentioned, it's a matter of "co-arising".</p>

<p><code>So, what should we focus on, in order to attain Nibbana?</code>
To put it in other words: "What's the right effort?"</p>

<p>To uphold right view, doing merits (10 kinds of them) and try to keep proper attention alive. </p>

<blockquote>
  <p>"One tries to abandon wrong view &amp; to enter into right view: This is one's right effort...</p>
  
  <p>"One tries to abandon wrong resolve &amp; to enter into right resolve: This is one's right effort...</p>
  
  <p>"One tries to abandon wrong speech &amp; to enter into right speech: This is one's right effort...</p>
  
  <p>"One tries to abandon wrong action &amp; to enter into right action: This is one's right effort...</p>
  
  <p>"One tries to abandon wrong livelihood &amp; to enter into right livelihood: This is one's right effort."</p>
  
  <p>— <a href="http://zugangzureinsicht.org/html/tipitaka/mn/mn.117.than_en.html" rel="nofollow noreferrer">MN 117</a></p>
</blockquote>

<p>Once right view is firm, the maintaining of proper attention (attention of what gives birth of phenomenas) is most importand to carry on.</p>

<p><code>Is it uprooting the craving or uprooting the ignorance?</code></p>

<p>When not-knowing is totally uprooted, craving has no more cause.</p>

<p><code>Because of what reason the uprooting of craving happen?
and
Because of what reason the uprooting of ignorance happen?</code></p>

<p>By the forth Noble truth, putting this very <a href="http://zugangzureinsicht.org/html/ptf/dhamma/sacca/sacca4/index_en.html" rel="nofollow noreferrer">Noble Eightfold path</a> into practice, follow it, not-knowing and craving finds it's end.</p>

<p><em>(Note that this is not given for trade, stacks, exchange or entertainment but to leave the bonds to this world)</em></p>
 254: <p>It's a "false dichotomy" to ask, "Is it this or that?" -- because it's both: they're related.</p>

<p>Given the "three poisons" (ignorance, desire, and aversion) I think that ignorance is described as the "root" of the other two -- it's because of ignorance that there's desire.</p>

<p>The word "ignorance" has a range of meanings: <a href="https://buddhism.stackexchange.com/q/26226/254">What is the difference between moha (delusion) and avijja (ignorance)?</a></p>

<p>I think that the four noble truths talk about the cessation of craving; and that the doctrine of the twelve nidanas say that craving is conditioned by sensation -- that it's caused or fuelled by e.g. "delighting" in pleasant sensations, aversion to unpleasant sensations, ignorance during neutral sensations.</p>

<p>So instead there should be "just seeing" and so on.</p>

<p>Another (more complicated) answer is that it's caused by habits or habitual tendencies, different kinds of desires and ignorance and wrong views: see for example <a href="https://buddhism.stackexchange.com/q/9414/254">What is effluent?</a></p>

<p>--</p>

<p>A more literal answer, I read that the 12 nidanas can be divided into groups:</p>

<ul>
<li>Causal process of previous life:

<ol>
<li>Ignorance</li>
<li>Sankharas</li>
</ol></li>
<li>Process of effect in the present life:

<ol start="3">
<li>Consciousness</li>
<li>Name-and-form</li>
<li>Six sense-bases</li>
<li>Contact</li>
<li>Feeling/sensation</li>
</ol></li>
<li>Causal process in the present life

<ol start="8">
<li>Greed</li>
<li>Appropriation</li>
<li>Becoming</li>
</ol></li>
<li>Process of effect of future life:

<ol start="11">
<li>Birth</li>
<li>Death</li>
</ol></li>
</ul>

<p>According to that model it's the link between 7 and 8 which you can affect, i.e. that where it's possible to "stop the wheel" -- because that's the part of it which happens in the present.</p>
