text: **Integrated information theory**
  
  Integrated information theory (IIT), developed by the neuroscientist and psychiatrist Giulio Tononi in 
  2004 and more recently also advocated by Koch, is one of the most discussed models of consciousness in 
  neuroscience and elsewhere.[135][136] The theory proposes an identity between consciousness and 
  integrated information, with the latter item (denoted as Φ) defined mathematically and thus in principle 
  measurable.[136][137] The hard problem of consciousness, write Tononi and Koch, may indeed be 
  intractable when working from matter to consciousness.[15] However, because IIT inverts this relationship 
  and works from phenomenological axioms to matter, they say it could be able to solve the hard 
  problem.[15] In this vein, proponents have said the theory goes beyond identifying human neural 
  correlates and can be extrapolated to all physical systems. Tononi wrote (along with two colleagues): 
  
  While identifying the "neural correlates of consciousness" is undoubtedly important, it is 
  hard to see how it could ever lead to a satisfactory explanation of what consciousness is and 
  how it comes about. As will be illustrated below, IIT offers a way to analyze systems of 
  mechanisms to determine if they are properly structured to give rise to consciousness, how 
  much of it, and of which kind.[138] 