There is nothing that we can cemently call 'Islam'-rather a number of things. Islam is:
1) 'Islamic scripture'
2) Islamic cultures
3) Islamic traditions
4) What Muslims believe Islam to be
5) How Muslims practice Islam
6) How leaders use Islam
7) How non-Muslims view Islam
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Political Islam
9) Military Islam
10) Domestic/home-based 'practical' Islam
Among other considerations-Islam is a range of factors-when people talk of Islam they usually refer to one of the factors above, like H.L.A Hart points out, conceptual analysis is a very complicated idea, and Islam is a concept, not just a simply ideology.