First Argument – This requires several introductions:
1) This world has a Creator/Lord
I’m not going to go into a long a deep discussion on the existence of a Creator God , just as the Holy Qur’an does not, and takes it as a matter of fact and something beyond doubt (Their messengers said: Can there be doubt concerning Allah, the Creator of the heavens and the earth? قَالَتْ رُسُلُهُمْ أَفِي اللَّـهِ شَكٌّ فَاطِرِ السَّمَاوَاتِ وَالْأَرْضِ). But this introduction is required to make the reader appreciate the fact that faith in a Creator is a necessity and above the need for proofs and debates, just like any other basic innate dispositions, as in the following verse, where ‘nature’ here means innate disposition:
فَأَقِمْ وَجْهَكَ لِلدِّينِ حَنِيفًا ۚ فِطْرَتَ اللَّـهِ الَّتِي فَطَرَ النَّاسَ عَلَيْهَا ۚ لَا تَبْدِيلَ لِخَلْقِ اللَّـهِ ۚ ذَٰلِكَ الدِّينُ الْقَيِّمُ وَلَـٰكِنَّ أَكْثَرَ النَّاسِ لَا يَعْلَمُونَ
So set thy purpose (O Muhammad) for religion as a man by nature upright – the nature (framed) of Allah, in which He hath created man. There is no altering (the laws of) Allah’s creation. That is the right religion, but most men know not. 
The next fundamental fact of existence is made clear in the next verse:
يَا أَيُّهَا النَّاسُ أَنتُمُ الْفُقَرَاءُ إِلَى اللَّـهِ ۖ وَاللَّـهُ هُوَ الْغَنِيُّ الْحَمِيدُ
O mankind! Ye are the poor in your relation to Allah. And Allah! He is the Absolute, the Owner of Praise.
The word ‘poor’ in arabic comes from the root meaning ‘the one whose spinal cord has been broken’, and who cannot ‘stand upright’ (exist) without the support (presence) of the Absolute (swt). All created beings are in constant need and cannot exist without the continuous support and guidance of Allah (swt). This is where our Imams of the Holy Household (‘as) have provided rational proof for the Necessary Being in their speeches and debates:
حدثنا أحمد بن محمد بن يحيى العطار (ره) قال: حدثنا سعد بن عبدالله، قال: حدثنا إبراهيم بن هاشم، عن علي بن معبد، عن الحسين بن خالد، عن أبي الحسن علي بن موسى الرضا عليهما السلام، أنه دخل عليه رجل فقال له: يا ابن رسول الله ما الدليل على حدث العالم؟ قال: أنت لم تكن ثم كنت، وقد علمت أنك لم تكون نفسك ولا كونك من هو مثلك
Imam Ali Al Ridha (‘as) said in a response to a question about the proof for the creation of the world: ‘You did not exist and now you exist, and you know that you did not create yourself, nor did someone like yourself create you.’
Then, the word Lord in Arabic gives meanings of ownership, guidance, wisdom, rearing and nurturing, which all refer to the role the Lord plays in providing and caring for his creation and the natural and spiritual development towards its intended goal of perfection.
قَالَ رَبُّنَا الَّذِي أَعْطَىٰ كُلَّ شَيْءٍ خَلْقَهُ ثُمَّ هَدَىٰ
He said: Our Lord is He Who gave unto everything its nature, then guided it aright.
2) The Creator is Just and Wise, and His actions have purpose:
Divine justice means that Allah does no injustice and in both of His creational and law-making systems acts according to what is right and fair, with no benefit or need to Himself, since he is the Absolute devoid of need and benefit, but to the benefit and well-being of His creation. Divine Justice is closely linked with His actions and the fact that all His actions have a purpose and a goal:
فَمَا زَالَت تِّلْكَ دَعْوَاهُمْ حَتَّىٰ جَعَلْنَاهُمْ حَصِيدًا خَامِدِينَ ﴿١٥﴾ وَمَا خَلَقْنَا السَّمَاءَ وَالْأَرْضَ وَمَا بَيْنَهُمَا لَاعِبِينَ ﴿١٦﴾ لَوْ أَرَدْنَا أَن نَّتَّخِذَ لَهْوًا لَّاتَّخَذْنَاهُ مِن لَّدُنَّا إِن كُنَّا فَاعِلِينَ ﴿١٧﴾ بَلْ نَقْذِفُ بِالْحَقِّ عَلَى الْبَاطِلِ فَيَدْمَغُهُ فَإِذَا هُوَ زَاهِقٌ ۚ وَلَكُمُ الْوَيْلُ مِمَّا تَصِفُونَ
We created not the heaven and the earth and all that is between them in play. (16) If We had wished to find a pastime, We could have found it in Our presence – if We ever did. (17) Nay, but We hurl the true against the false, and it doth break its head and lo! it vanisheth. And yours will be woe for that which ye ascribe (unto Him).
3) The goal of the creation of Man is happiness in both abodes :
No doubt that the goal of creation of Man is for him to reach purity of the soul and nearness to Allah (swt), through reflection of true divine unity in his essence, character and actions, and this is the true perfection.
This does not mean that there aren’t other intermediate and prerequisite goals other than nearness to Allah (swt) for Man, like his happiness in the hereafter, which give further evidence to Allah’s mercy and justice to humanity, providing him with an eternal life after a short period of struggle, and a place of accountability for their actions.
أَفَحَسِبْتُمْ أَنَّمَا خَلَقْنَاكُمْ عَبَثًا وَأَنَّكُمْ إِلَيْنَا لَا تُرْجَعُونَ
What! did you then think that We had created you in vain and that you shall not be returned to Us?
Therefore, belief in a wise, just Creator cannot be complete if not accompanied by the faith in the return to Him on the day of judgement.
In my next post I will put forth some of Man’s unique characteristics that need clarifying before moving onto the next introduction.
 A detailed discussion of this subject can be found in Seyyed Kamal Al Haydari’s books ‘Divine Unity’ and ‘Divine Justice’ in arabic, and in many of Martyr Mutahhari’s writings available in English.
 توحيد الصدوق , pg 293 (arabic version)
 And the verses dealing with the hereafter are numerous and detailed, some of them are: 50:35, 11:108, 15:48, 14:57, 56:32-33