I do remember some theories concerning relativity suggesting some sort of motion in space might allow time travel if space-time geometrics are possible.
Let us consider some common phenomena in the light of these rival theories as to the nature of matter.
To this attitude he offered uncompromising opposition, and by the synthetical production of numerous hydrocarbons, natural fats, sugars and other bodies he proved that organic compounds can be formed by ordinary methods of chemical manipulation and obey the same laws as inorganic substances, thus exhibiting the "creative character in virtue of which chemistry actually realizes the abstract conceptions of its theories and classifications - a prerogative so far possessed neither by the natural nor by the historical sciences."
Even at this stage the vindictive or retributive character of punishment remains, but gradually, and specially after the humanist movement under thinkers like Beccaria and Jeremy Bentham, new theories begin to emerge.
Modern theories date from the 18th century, when the humanitarian movement began to teach the dignity of the individual and to emphasize his rationality and responsibility.
How would you define theories? Add your definition here.