user13694: In the paticcasamuppada's formulation of the twelve nidanas, vedana precedes tanha. 
As far as I currently understand, vedana is just the physiological and psychological -and involuntary- response 
(felt as a pleasent, unpleasent or neutral sensation) to an specific stimulus. Vedana by itself shouldn't be an enough condition to give rise to tanha, because there's no necessarily an evaluation (sañña) of that feeling that could lead to the rise of a preference (like, dislike or neither-like-nor-dislike), and consequently, to the rise of tanha.
If read in this fashion, shouldn't be sañña placed between vedana and tanha?
Thanks in beforehand.

user11009: Vedana and Sanna are conjoined not disjoint.
When it says Vedan it implies there is Sanna as well.
=============
"Feeling, perception, & consciousness, friend: Are these qualities conjoined or disjoined? Is it possible, having separated them one from another, to delineate the difference among them?"
"Feeling, perception, & consciousness are conjoined, friend, not disjoined. It is not possible, having separated them one from another, to delineate the difference among them. For what one feels, that one perceives. What one perceives, that one cognizes. Therefore these qualities are conjoined, not disjoined, and it is not possible, having separated them one from another, to delineate the difference among them."
https://www.accesstoinsight.org/tipitaka/mn/mn.043.than.html

user43: In paticcasamuppada, shouldn't sañña precede tanha, instead of vedana?
It should and it does: vedana => sañña => vitakka => papanca.
From Madhupindika Sutta (MN 18):

With contact as a requisite condition, there is feeling (vedana). What one feels, one perceives (sañña). What one perceives, one thinks (vitakka) about. What one thinks about, one objectifies (papanca). 

To clarify terms, vedana is the qualitative component of the experience of subjective contact with a subjectively delineated (mental representation of) object: "this object feels right" / "this object feels wrong" / "this object feels neither right nor wrong".
Sañña is recognition/classification/delineation of a (subjective notion of) object by the raw features (signs) available to direct observation. While described as a single step, in actuality it is a chain of inferences that evaluates the signs, puts forward hypotheses about the perceived entity and feeds back to seeking more signs to confirm the hypothesis. At the advanced phases of the inference chain, sañña reaches a level of abstraction when it can be described as "conceptualization".
Vitakka (in this context) is pondering or mulling over. It is bringing the attention again and again to a given idea.
Papanca is entering a relationship of "pursuer & pursued" (or acquirer and acquired) with regard to an object. It is objectifying something and making it one's goal (-- and implicitly, making oneself an agent of pursuit. This is out of scope for this question but this is exactly how bhava or "becoming a personal form of existence" comes to fruition).
So, first we delineate an object, then we attribute pleasant experience to a contact with the object, then we conceptualize this experience of contact and the resulting feeling and make it into a target we'd like to acquire.  

13694: <p>In the paticcasamuppada's formulation of the twelve nidanas, vedana precedes tanha. </p>

<p>As far as I currently understand, vedana is just the physiological and psychological -and involuntary- response 
(felt as a pleasent, unpleasent or neutral sensation) to an specific stimulus. Vedana by itself shouldn't be an enough condition to give rise to tanha, because there's no necessarily an evaluation (sañña) of that feeling that could lead to the rise of a preference (like, dislike or neither-like-nor-dislike), and consequently, to the rise of tanha.</p>

<p>If read in this fashion, shouldn't be sañña placed between vedana and tanha?</p>

<p>Thanks in beforehand.</p>
 11009: <p>Vedana and Sanna are conjoined not disjoint.
When it says Vedan it implies there is Sanna as well.</p>

<p>=============</p>

<p>"Feeling, perception, &amp; consciousness, friend: Are these qualities conjoined or disjoined? Is it possible, having separated them one from another, to delineate the difference among them?"</p>

<p>"Feeling, perception, &amp; consciousness are conjoined, friend, not disjoined. It is not possible, having separated them one from another, to delineate the difference among them. For what one feels, that one perceives. What one perceives, that one cognizes. Therefore these qualities are conjoined, not disjoined, and it is not possible, having separated them one from another, to delineate the difference among them."</p>

<p><a href="https://www.accesstoinsight.org/tipitaka/mn/mn.043.than.html" rel="nofollow noreferrer">https://www.accesstoinsight.org/tipitaka/mn/mn.043.than.html</a></p>
 43: <h2>In paticcasamuppada, shouldn't sañña precede tanha, instead of vedana?</h2>

<p>It should and it does: vedana => sañña => vitakka => papanca.</p>

<p>From Madhupindika Sutta (MN 18):</p>

<blockquote>
  <p>With contact as a requisite condition, there is feeling (vedana). What one feels, one perceives (sañña). What one perceives, one thinks (vitakka) about. What one thinks about, one objectifies (papanca). </p>
</blockquote>

<p>To clarify terms, vedana is the qualitative component of the experience of subjective contact with a subjectively delineated (mental representation of) object: "this object feels right" / "this object feels wrong" / "this object feels neither right nor wrong".</p>

<p>Sañña is recognition/classification/delineation of a (subjective notion of) object by the raw features (signs) available to direct observation. While described as a single step, in actuality it is a chain of inferences that evaluates the signs, puts forward hypotheses about the perceived entity and feeds back to seeking more signs to confirm the hypothesis. At the advanced phases of the inference chain, sañña reaches a level of abstraction when it can be described as "conceptualization".</p>

<p>Vitakka (in this context) is pondering or mulling over. It is bringing the attention again and again to a given idea.</p>

<p>Papanca is entering a relationship of "pursuer &amp; pursued" (or acquirer and acquired) with regard to an object. It is objectifying something and making it one's goal (-- and implicitly, making oneself an agent of pursuit. This is out of scope for this question but this is exactly how <em>bhava</em> or "becoming a personal form of existence" comes to fruition).</p>

<p>So, first we delineate an object, then we attribute pleasant experience to a contact with the object, then we conceptualize this experience of contact and the resulting feeling and make it into a target we'd like to acquire.  </p>
