In dictionaries Default is identified as: a situation or condition that obtains in the absence of active intervention. There are a lot of examples to this default in Islam:
1- A creator: since we did not prove that existence can come from not existence we have to believe there is a creator.
2- One creator: since the laws of cosmos do not contradict with one another or change over time there is no good evidence to support more than one creator.
3- Prophethood: There is no proofs of the prophets were liars. They were few chosen from billions of peoples and they were proved to be honest and disproved to be liars. The default here is they are not liars and they are the medium or the connection between God and us.
4- Islam: since people failed to prove lies against Muhammad (PBUH) and continue to fail to come up with a book like the Quran, Islam by default is true. You are invited to disprove it, help yourself read the Quran but if you fail then you have to accept it.
5- Spiritually: humans have the inborn desire to worship one God and to live with him and by him. This relationship even gets stronger than our relationship with our family members. The spiritual feeling and experience is too strong that is we can not disprove it and do not have the means even to disprove it. If someone decided to astray from God with his mind and soul it does not prove to us that there is no human spirituality.
6- After life: According to Islam: Humans are by default entitled to inhabitat heaven if they would submit to God's messages. Active denial, arrogance and resisting are against the inner cry of their souls to find God and in their inheritance of God's spirit to be righteous. If you can not disprove there is no after life by default there is after life for a lot of people since many connect with their dead family members through visions including me.
7- God's wrath: is the default before he send most of his messengers. The wickedness of humans commonly preceded the coming of his messengers. This takes several forms like widespread denial of God or widespread injustices and corruptions. Same with the second coming of Jesus. Thus when God send warning before his wrath we have to respect that and read the book of revelation.
8- The default at the day of judgment is no intercession to the disbelievers ( it is God compassion that there will be intercession to the believers). It is not discrimination against them they did discriminate against their God and despite all his power and Glory and they denied him. They acknowledged a single flower and a small mouse and denied their creator or worships some of his creation. They worshiped cow and other animals and denied him.
9- Existence of Satan: by default since the evil that people do despite the good pays more and the common good that is they are missing tell you loudly there is Satan. You do not have evidences to refute that he is real.