Derive the Purpose of Life without Divine Text?

Is knowing the purpose of life a priori knowledge or must it be posteriori via revelation or whimsical determination? I would like to say it can be a priori because it can be derived from reason independent of revelation, however it is tedious. The argument follows from the kalam cosmological argument and the necessary attributes of the uncreated creator (particularly wisdom) as referenced in chapter 5, ‘A Universe from Nothing?’ of the book, the Divine Reality by Hamza Tzortzis. From this the following argument is made:

Argument 1: We aren't useless.

Premise 1: An all-knowing, wise God exists

Premise 2: It is not wise to create something useless/functionless/purposeless

Premise 3: We were created

Conclusion: Therefore, we are created by God with a purpose.

I can elaborate a bit on the premises:

1. An all knowing, wise God exists
1. The issue that he is all knowing is evident from the complexity of the world around us and the regularity and stability at which it exists. This is evident because it has laws, in Hamza’s words, “These include the law of gravity, the weak and strong nuclear force, and the electromagnetic force”.
2. The issue of whether he is wise is evident because humans have wisdom, this is because, “A thing cannot give rise to something else if it does not contain it, or if it does not have the ability to give rise to it” (57 Tzortzis). Because (some) humans are wise, the agent that gave wisdom to humans must have wisdom as well. This is assuming emergent materialism is false (60 Tzortzis).
3. We cannot have more positive attributes than God because God cannot create a being more perfect than Himself. Therefore, if we consider ourselves wise enough, we must consider God to be infinitely more wise.
2. It is not wise to create something useless/functionless/purposeless.
1. A child creates out of clay figurines with seemingly no purpose.
1. Is the purpose to entertain oneself? If so that is not very wise
2. Humans create things with a purpose, look around you, the computer, the lights, the air conditioning, the house, your phone, this text you are reading, all are created with a purpose, they are all useful.
3. It is impossible for the creation of the creator to be more wise than the creator itself. This is because the creator is perfect, and therefore it cannot create something more perfect than itself. If we think that to create something useless is unwise, and God cannot be unwise, then God cannot create something useless.
3. We were created.
1. Created in the sense that we, at one point, did not exist and now we do exist in an objective sense.

Therefore God did not create us functionless/purposeless/useless.

Then did you think that We created you uselessly and that to Us you would not be returned?" 

-23:115 Quran

We would develop conditions to help us figure out what might this purpose be.

Argument 2: Our purpose is to revere Him.

Premise 1: There are conditions as to what this purpose might be

Premise 2: The only relationship that can exist from these conditions is a relationship of gratitude

Premise 3: The ultimate form of gratitude is reverence

Conclusion: God created us to revere him.

1. Premise 1: There are conditions as to what this purpose might be
1. Condition 1: The creator created us for a purpose; this follows from the previous argument
2. Condition 2: Since He created with a purpose, this purpose must involve Him somehow.
1. To create something whose purpose is to benefit His other creation is redundant because he could have created His other creation as self sufficient
2. Any ultimate purpose that does not involve him is useless
3. God does not create useless entities
4. Should we accept this condition, since we know that all things were created by Him, all things have a purpose/use/function, and therefore all things are associated somehow with Him.
3. Condition 3: We must be able to do something that God cannot do without our existence and this ability is part of the purpose.
1. This might seem impossible and outright blasphemous but we can do things that God cannot. We can create rocks that we cannot move; God cannot (because God has power over all things). We can die; God cannot. We can sin; God cannot. We can worship God; God cannot worship himself.
4. Condition 4: We cannot benefit God, We cannot add to his greatness or glory because He is needless and we cannot "add a finite to an infinity"

Although it seems as though condition 2 and condition 4 contradict because the following contention can be raised,  "If the creator is self-sufficient and unlimited, then why would he even create anything if it cannot, by definition, benefit him?" From the Islamic perspective, this has already been raised and dealt with. The angels posed this question in some form to God within the Quran.

[Prophet], when your Lord told the angels, ‘I am putting a successor on earth,’ they said, ‘How can You put someone there who will cause damage and bloodshed, when we celebrate Your praise and proclaim Your holiness?’ but He said, ‘I know things you do not.’

-2:30

In other words, God's intention as to why he created us will remain unknown, but we know that he created us with a use/function/purpose. 

1. Premise 2: The only relationship that can exist from these conditions is a relationship of gratitude
1. We are now put into a association with the divine in which we are only in a position to receive. The purpose could be to enjoy these gifts that we receive and ignore the link, but that would make us purposeless as the 'link' is non-existent (condition 2).

   
   
   The only link that is fathomable and fulfills all conditions is a link of gratitude. No matter how hard we try we can never give back to God in our relationship with Him. As such the only relationship we can participate is that of gratitude. He will keep on giving and we are incapacitated in making any meaningful return.
2. Premise 3: The ultimate form of gratitude is reverence
1. The ultimate form of gratitude is reverence and worship. At the first stage of gratitude, we must recognize that all we receive from God is from him alone and no one else. The next stage of gratitude towards the ultimate being for the ultimate gift of life should be the ultimate form of gratitude: worship and reverence.

Worship, from the Islamic perspective, includes following commandments (being dutiful to one’s parents, Hajj, Zakat, etc.), utilizing your gift of life in the way He instructed, actually worshiping him in prayer, praising His name, and having a sense of reverence and awe in your heart. Creating and aiding His other creation in His worship as well. This implies helping your co-creation live healthy, long, enjoyable lives and having children that continue to worship Him for it is their purpose. Yet they should be living lives in God's reverence and should be encouraging people to recognize that God is worthy of worship along with yourself! However, this does not mean to live in a closet like an ascetic, but to properly follow the commands of your Lord, and some include obtaining the bounties of this life through honest work!

So, when the prayer is accomplished, then spread abroad in the land, and seek of the Grace of Allah, and remember Allah much, that possibly you would prosper.

-62:10

Subhanallah, Allahu Akbar, it is to recite these phrases for which we were created!