Here are some relevant quotes on this topic:
Ven. K. Nanananda:
Phassa - Contact: A hybrid between 'Verbal Impression' (adhivacana-samphassa) and 'Resistance Impression' (paṭigha-samphassa).
One can form an idea about the relation between name-and-form and consciousness by going deeper into the implications of this discourse. In the discussion of the interrelation between name and form, the Buddha makes use of two highly significant terms, namely adhivacanasamphassa and paṭighasamphassa. How contact arises dependent on name-and-form is explained by the Buddha in the MahāNidānasutta of the Dīgha Nikāya.
It is addressed to Venerable Ānanda in the form of a catechism.
Phassa, or contact, is a sort of hybrid, carrying with it the implications of both adhivacanasamphassa and paṭighasamphassa. That is to say, it partakes of the character of name, nāma, as suggested by adhivacanasamphassa, as well as that of form, rūpa, indicated by paṭighasamphassa. This will be clear from the relevant section of the catechism in the MahāNidānasutta:
'Nāmarūpapaccayā phasso'ti iti kho panetaṃ vuttaṃ, tad'Ānanda, imināpetaṃ pariyāyena veditabbaṃ, yathānāmarūpapaccayā phasso. Yehi, Ānanda, ākārehi yehi liṅgehi yehi nimittehi yehi uddesehi nāmakāyassa paññatti hoti, tesu ākāresu tesu liṅgesu tesu nimittesu tesu uddesesu asati api nu kho rūpakāye adhivacanasamphasso paññāyethā'ti?' 'No hetaṃ, bhante.'
'Yehi, Ānanda, ākārehi yehi liṅgehi yehi nimittehi yehi uddesehi rūpakāyassa paññatti hoti, tesu ākāresu tesu liṅgesu tesu nimittesu tesu uddesesu asati api nu kho nāmakāye paṭighasamphasso paññāyethā'ti?' 'No hetaṃ, bhante.'
'Yehi, Ānanda, ākārehi yehi liṅgehi yehi nimittehi yehi uddesehi nāmakāyassa ca rūpakāyassa ca paññatti hoti, tesu ākāresu tesu liṅgesu tesu nimittesu tesu uddesesu asati api nu kho adhivacanasamphasso vā paṭighasamphasso vāpaññāyethā'ti?' 'No hetaṃ, bhante.'
'Yehi, Ānanda, ākārehi yehi liṅgehi yehi nimittehi yehi uddesehi nāmarūpassa paññatti hoti, tesu ākāresu tesu liṅgesu tesu nimittesu tesu uddesesu asati api nu kho phasso paññāyethā'ti?' 'No hetaṃ, bhante.' 'Tasmātih'Ānanda, eseva hetu etaṃ nidānaṃ esa samudayo esa paccayo phassassa, yadidaṃ nāmarūpaṃ.'
"From name-and-form as condition, contact comes to be. Thus it has been said above. And that Ānanda, should be understood in this manner, too, as to how from name-and-form as condition, contact arises. If, Ānanda, all those modes, characteristics, signs and exponents, by which the name-group, nāma-kāya, is designated were absent, would there be manifest any verbal impression, adhivacanasamphassa, in the form-group, rūpa-kāya?" "There would not, lord."
"If, Ānanda, all those modes, characteristics, signs and exponents, by which the form-group is designated were absent, would there be manifest any resistance-impression, paṭighasamphasso, in the name-group?" "There would not, lord."
"And if, Ānanda, all those modes, characteristics, signs and exponents, by which there is a designation of both name-group and form-group were absent, would there be manifest either any verbal impression or any resistance-impression?" "There would not, lord."
"And if, Ānanda, all those modes, characteristics, signs and exponents, by which there comes to be a designation of name-and-form were absent, would there be manifest any contact?" "There would not, lord." "Wherefore, Ānanda, this itself is the cause, this is the origin, this is the condition for contact, that is to say, name-and-form."
With the help of four words of allied sense, namely ākāra, mode, liṅga, characteristic, nimitta, sign, and uddesa, exponent, the Buddha catechetically brings out four conclusions by this disquisition. They are:
1) By whatever modes, characteristics, signs and exponents the name-group, nāma-kāya, is designated, in their absence no designation of verbal impression, adhivacanasamphassa, in the form-group, rūpa-kāya, is possible.
2) By whatever modes, characteristics, signs and exponents the form-group is designated, in their absence no designation of resistance-impression, paṭighasamphasso, in the name-group, nāmakāya, is possible.
3) By whatever modes, characteristics, signs and exponents both name-group and form-group are designated, in their absence no designation of verbal impression or resistance-impression is possible.
4) By whatever modes, characteristics, signs and exponents name-and-form is designated, in their absence no designation of contact is possible.
What we have here is adhivacanasamphassa. Its affinity to name is obvious, and this is precisely the meaning we attributed to nāma. Therefore, what we have in this concept of nāmakāya, or name-group, literally 'name-body', is a set of first principles in linguistic usage pertaining to definition.
The form-group, or rūpakāya, literally 'form-body', on the other hand has something to do with resistance, as suggested by the term paṭighasamphassa. Paṭigha means 'striking against'. Form, or rūpa, has a striking quality, while name, or nāma, has a descriptive quality. Phassa, or contact, is a hybrid of these two. This is what gives a deeper dimension to the above disquisition.
The point that the Buddha seeks to drive home is the fact that the concept of contact necessarily presupposes both name and form. In other words, name and form are mutually interrelated, as already stated above. There would be no verbal impression in the form-group, if there were no modes, characteristics, etc., proper to name. Likewise there could be no resistant impression in the name-group, if there were no modes, characteristics, etc., proper to form.
At first sight these two may appear as totally opposed to each other. But what is implied is a case of mutual interrelation. The expression peculiar to the name-group is a necessary condition for the form-group, while the resistance peculiar to the form-group is a necessary condition for the name-group. Since here we have something deep, let us go for an illustration for the sake of clarity.
As we have already stated, a verbal impression in regard to the form-group is there because of the constituents of the name-group. Now the form-group consists of the four great primaries earth, water, fire and air. Even to distinguish between them by their qualities of hardness and softness, hotness and coolness, etc., feeling, perception, intention, contact and attention, which are the constituents of the name-group, have to play their part. Thus it is with the help of those members on the name side that the four basic elements associated with form receive recognition.
Interest, attention and contact together bring out some deeper implications of the law of dependent arising. Not only with regard to inanimate objects, but even in the case of this conscious body, the question of contact is related to the fact of attention.
If, for instance I ask what I am touching now, one might say that I am touching the palm leaf fan in my hand. This is because we usually associate the idea of touching with the hand that holds. But suppose I put away the fan and ask again what I am touching now, one might find it difficult to answer. It might not be possible for another to guess by mere external observation, since it is essentially subjective. It is dependent on my attention. It could even be my robe that I am touching in the sense of contact, in which case I am becoming conscious of my body as apart from the robe I am wearing.
Consciousness follows in the wake of attention. Whatever my attention picks up, of that I am conscious. Though I have in front of me so many apparently visible objects, until my attention is focused, eye-consciousness does not come about. The basic function of this type of consciousness, then, is to distinguish between the eye and the object seen. It is only after the eye has become conscious, that other factors necessary for sense perception fall into place.
The two things born of that basic discrimination, together with the discriminating consciousness itself, that is eye-consciousness, make up the concept of contact. Cakkhuñca paṭicca rūpe ca uppajjati cakkhuviññāṇaṃ, tiṇṇaṃ saṅgati phasso. "Dependent on eye and forms, eye-consciousness arises, the concurrence of the three is contact."
Let us now consider how resistance-impression, paṭighasamphassa, comes about. It is said that the factors of the form-group have a part to play in producing resistance-impression on the name-group. We sometimes speak of an idea 'striking us', as if it were something material. Or else an idea could be 'at the back' of our mind and a word 'on the tip' of our tongue.
The clearest manifestation of contact is that between material objects, where collision is suggestive of resistance, as implied by the word paṭigha. This primary sense of striking against or striking together is implicit even in the simile given by the Buddha in the Dhātuvibhaṅgasutta of the Majjhima Nikāya, and in the Phassamūlakasutta of the Saṃyutta Nikāya, concerning two sticks being rubbed together to kindle a fire.
Though as a gross manifestation contact is primarily associated with the form-group, it is essentially connected with the name-group, as we have already explained with illustrations. It is when both resistance-impression and verbal impression come together that contact arises, dependent on name-and-form, nāmarūpapaccayā phasso.
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Kalupahana, in explicating the Buddha's teaching phenomenologically, writes the following: "... when the question regarding the nature of mind (nama) and matter (rupa) was raised, he responded by saying that the so-called matter is 'contact with resistence' (patigha-samphassa) and what is called mind is 'contact with concepts' (adhivacana-samphassa). In doing so, he was reducing both mind and matter to contact (samphassa) and, therefore, processes of experience rather than any kind of material-stuff or mind-stuff." (The Principles of Buddhist Philosophy)
MINDFULNESS IS DIFFICULT BECAUSE PHASSA IS NOTED ON ONLY ONE LEVEL.
The problem is that it is difficult to note anatta in the arammana (objects) that strike (the senses). This is because we don't know how to note both levels of phassa (contact). The level of patigha-samphassa (sensory contact) is to be aware merely of color or sound; once there is adhivacana-samphassa (designating contact) the meaning or value is known. Right here it is possible for sati (mindfulness) to note the fact of anatta in time. We consider patigha-samphassa to be "literal" and adhivacana-samphassa to be "essential." There's enough of a chance to note anatta in the nick of time.
‘Being touched’ is a formation; contact/impression (phassa) is an activity that modifies and colours the sense of self. In this respect, I’m referring not so much to direct sensory contact or ‘impingement contact’ (patigha-phassa), but the impression that the mind makes of that contact, called ‘designation contact’ (adhivacana-phassa). This form of contact is the significant one: owing to the subjective flavouring of designation contact, different people find different sights, sounds, flavours, ideas, remarks and gestures delightful, repugnant, or neutral. Designation contact sets up the familiar pattern of how we experience the world; and the consequent perceptions and impressions guide what we will make impingement contact with in the future. So this is the key to how we react and create fresh action, or kamma, based on the blueprint of the past. (Only to discover that what was wonderful once becomes ‘same old thing’ the third time round.)