1. A method for identifying a chemical substance from a set of output states provided by a chemical sensor array being exposed to the chemical substance, the method comprising: selecting, with an evaluation circuit, from a set of class descriptions for different chemical substances a first class description and one or more further class descriptions, wherein the first class description is related to a first chemical substance and a further class description is related to a further chemical substance; estimating, with one or more estimating units, a first likelihood value and one or more further likelihood values, wherein the first likelihood value represents a probability that the set of output states corresponds to the first class description, and a respective further likelihood value represents a probability that the set of output states corresponds to a respective further class description; and determining, with a processing means, from the estimated first and further likelihood values the class description with a highest likelihood value, wherein the estimating of the first likelihood value and one or more further likelihood values includes combining likelihood values estimated for at least two subsets of the set of output states corresponding to the first and further class description, respectively, said set of output states contains an over-determined set of output states, and at least one of the first likelihood value or the further likelihood values is formed by a sum of a likelihood value obtained for a triplet of output states with a first weighted sum of likelihood values obtained for all possible pairs of output states contained in the triplet of output states, each of said pairs constituting a subset, and each output state of the triplet of output states originates from a different sensor of the chemical sensor array and a possible pair of output states is given by any two individual output states of the triplet of output states.