Allah says that these antonyms are clearly not equal, the blind and the seeing are not equal, there is a difference and a huge gap between them. Darkness and light are not equal, neither are shade and the sun's heat. By the same token, the living and the dead are not equal. This is the parable Allah makes of the believers who are the living, and the disbelievers who are the dead. This is like the Ayat:
[أَوَمَن كَانَ مَيْتًا فَأَحْيَيْنَـهُ وَجَعَلْنَا لَهُ نُورًا يَمْشِي بِهِ فِى النَّاسِ كَمَن مَّثَلُهُ فِي الظُّلُمَـتِ لَيْسَ بِخَارِجٍ مِّنْهَا كَذَلِكَ]
(Is he who was dead and We gave him life and set for him a light (of belief) whereby he can walk amongst men -- like him who is in the (depths of) darkness from which he can never come out) (6:122),
[مَثَلُ الْفَرِيقَيْنِ كَالاٌّعْمَى وَالاٌّصَمِّ وَالْبَصِيرِ وَالسَّمِيعِ هَلْ يَسْتَوِيَانِ مَثَلاً]
(The parable of the two parties is as that of the blind and the deaf and the seer and the hearer. Are they equal when compared) (11:24) The believer sees and hears, and walks in the light upon a straight path in this world and the Hereafter, until he comes to settle in Gardens (Paradise) wherein is shade and springs. The disbeliever is blind and deaf, walking in darkness from which he cannot escape, he is lost in his misguidance in this world and the Hereafter, until he ends up in fierce hot wind and boiling water, and shadow of black smoke, neither cool nor good.
[إِنَّ اللَّهَ يُسْمِعُ مَن يَشَآءُ]
(Verily, Allah makes whom He wills to hear,) means. He guides them to listen to the proof and accept it and adhere it.
[وَمَآ أَنتَ بِمُسْمِعٍ مَّن فِى الْقُبُورِ]
(but you cannot make hear those who are in graves.) means, `just as the dead cannot benefit from guidance and the call to truth after they have died as disbelievers and ended up in the graves, so too you cannot help these idolators who are decreed to be doomed, and you cannot guide them.'
Clearly the verse you cited is about disbelievers. Allah gives some examples of extreme opposites such as light and dark. In the same way Allah gives the extreme opposite to believers in the form of disbelievers. The believer has the ability to hear and see in this world and the hereafter i.e. he enjoys the light of the straight path until he settles in heaven. The disbeliever is deaf and blind in this world and the hereafter i.e. he cannot escape from walking in the darkness until he goes to hell.
Allah speaks to the Prophet and says the disbeleivers cannot be helped or be guided. For this Allah gives the example JUST LIKE THE DISBELEIVERS WHO ARE DEAD AND ARE IN THEIR GRAVES CANNOT BENEFIT FROM GUIDANCE AND CALLS TO THE TRUTH, IN THE SAME WAY THE IDOLATORS CANNOT BE GUIDED. In the next verse Allah says that the Prophet is a warner to the disbeleivers and the bearers of glad tidings to the beleivers.
Thus these verses are to ascertain the distinction between believers and disbeleivers. Ultimately the disbeleivers cannot be guided but merely warned. Thus the verse is not sufficent and applicable proof/evidence that the dead cannot hear/see/help etc.
VERSE 2
"Verily you cannot make the dead hear and you can not make the deaf hear the call when they turn their backs and retreat." [Surah an-Naml 27:80]
Again I have attempted to give the reader some background information which precedes the verse you cited above.
Allah tells us about His Book and the guidance, proof and criterion between right and wrong that it contains. He tells us about the Children of Israel, who were the bearers of the Tawrah and Injil. How they had different opinions about `Isa. The Jews lied about him while the Christians exaggerated in praise for him, so the Qur'an came with the moderate word of truth and justice: that he was one of the servants of Allah, and one of His noble Prophets and Messengers, may the best of peace and blessings be upon him. Allah says the holy books are a guidance for believers His servants do and say. Allah goes on to say that he will take vengance against those who exaggerated and lied about the books. Allah then says to the Prophet (pbuh) that continue to convey the message of his Lord. The ending portion of this verse is as followed:
[إِنَّكَ عَلَى الْحَقِّ الْمُبِينِ]
(surely, you are on manifest truth.) meaning, you are following manifest truth, even though you are opposed by those who oppose you because they are doomed. The Word of your Lord has been justified against them, so that they will not believe even if all the signs are brought to them. Allah says:
[إِنَّكَ لاَ تُسْمِعُ الْمَوْتَى]
(Verily, you cannot make the dead to hear) meaning, you cannot cause them to hear anything that will benefit them. The same applies to those over whose hearts is a veil and in whose ears is deafness of disbelief. Allah says:
[وَلاَ تُسْمِعُ الصُّمَّ الدُّعَآءَ إِذَا وَلَّوْاْ مُدْبِرِينَ]
وَمَآ أَنتَ بِهَادِى الْعُمْىِ عَن ضَلَـلَتِهِمْ إِن تُسْمِعُ إِلاَّ مَن يُؤْمِنُ بِـئَايَـتِنَا فَهُم مُّسْلِمُونَ-]
(nor can you make the deaf to hear the call, when they flee, turning their backs. Nor can you lead the blind out of their error. You can only make to hear those who believe in Our Ayat, so they submit (became Muslims).) meaning, those who have hearing and insight will respond to you, those whose hearing and sight are of benefit to their hearts and who are humble towards Allah and to the Message that comes to them through the mouths of the Messengers, may peace be upon them.
This verse you have cited is also in relation to disbeleivers. Allah is saying to the prophet (pbuh) those who will have light will respond and those who are in darkness will not respond to you just like the disbeleivers in their graves. Allah will take his vengance on the disbeleivers.
I hope this has clarified the interpretations of these two verses you have cited. Again I would like to reiterate it is important that we do not interpret the Quran without weighing up the sources and applying the relevant islamic normative sciences.
May Allah keep us on the straight path
Maximus