diff --git a/CMakeLists.txt b/CMakeLists.txt
index 91811264c..43159a935 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,14 +6,10 @@ if(NOT DEFINED CMAKE_MACOSX_RPATH)
   set(CMAKE_MACOSX_RPATH 0)
 endif()
 
-option(GTSAM_NO_BOOST_CPP17 "Require and use boost" ON)
 add_definitions(-Wno-deprecated-declarations)
 add_definitions(-ftemplate-backtrace-limit=0)
 
 set(CMAKE_CXX_STANDARD 17)
-if (GTSAM_NO_BOOST_CPP17)
-  add_definitions(-DNO_BOOST_CPP17)
-endif()
 
 # Set the version number for the library
 set (GTSAM_VERSION_MAJOR 4)
@@ -60,10 +56,7 @@ endif()
 include(cmake/HandleGeneralOptions.cmake)   # CMake build options
 
 # Libraries:
-# if (NOT GTSAM_NO_BOOST_CPP17)
-  include(cmake/HandleBoost.cmake)            # Boost
-# endif()
-  
+include(cmake/HandleBoost.cmake)            # Boost
 include(cmake/HandleCCache.cmake)           # ccache
 include(cmake/HandleCPack.cmake)            # CPack
 include(cmake/HandleEigen.cmake)            # Eigen3
diff --git a/gtsam/nonlinear/ExpressionFactor.h b/gtsam/nonlinear/ExpressionFactor.h
index 3427e6079..650bedfb1 100644
--- a/gtsam/nonlinear/ExpressionFactor.h
+++ b/gtsam/nonlinear/ExpressionFactor.h
@@ -28,97 +28,6 @@
 
 namespace gtsam {
 
-template <typename... ValueTypes>
-class EvaluateErrorInterface {
-public:
-  enum { N = sizeof...(ValueTypes) };
-
-private:
-  template <int I>
-  using IndexIsValid = typename std::enable_if<(I >= 1) && (I <= N),
-                                               void>::type;  // 1-indexed!
-
-public:
-  /**
-   * Override `evaluateError` to finish implementing an n-way factor.
-   *
-   * Both the `x` and `H` arguments are written here as parameter packs, but
-   * when overriding this method, you probably want to explicitly write them
-   * out.  For example, for a 2-way factor with variable types Pose3 and Point3,
-   * you should implement:
-   * ```
-   * Vector evaluateError(
-   *     const Pose3& x1, const Point3& x2,
-   *     boost::optional<Matrix&> H1 = boost::none,
-   *     boost::optional<Matrix&> H2 = boost::none) const override { ... }
-   * ```
-   *
-   * If any of the optional Matrix reference arguments are specified, it should
-   * compute both the function evaluation and its derivative(s) in the requested
-   * variables.
-   *
-   * @param x The values of the variables to evaluate the error for.  Passed in
-   * as separate arguments.
-   * @param[out] H The Jacobian with respect to each variable (optional).
-   */
-  virtual Vector evaluateError(const ValueTypes&... x, OptionalMatrixTypeT<ValueTypes>... H) const = 0;
-
-#ifdef NO_BOOST_CPP17
-  // if someone uses the evaluateError function by supplying all the optional
-  // arguments then redirect the call to the one which takes pointers
-  Vector evaluateError(const ValueTypes&... x, MatrixTypeT<ValueTypes>&... H) const {
-    return evaluateError(x..., (&H)...);
-  }
-#endif
-
-  /// @}
-  /// @name Convenience method overloads
-  /// @{
-
-  /** No-Jacobians requested function overload.
-   * This specializes the version below to avoid recursive calls since this is
-   * commonly used.
-   *
-   * e.g. `const Vector error = factor.evaluateError(pose, point);`
-   */
-  inline Vector evaluateError(const ValueTypes&... x) const {
-    return evaluateError(x..., OptionalMatrixTypeT<ValueTypes>()...);
-  }
-
-  /** Some (but not all) optional Jacobians are omitted (function overload)
-   *
-   * e.g. `const Vector error = factor.evaluateError(pose, point, Hpose);`
-   */
-  template <typename... OptionalJacArgs, typename = IndexIsValid<sizeof...(OptionalJacArgs) + 1>>
-  inline Vector evaluateError(const ValueTypes&... x, OptionalJacArgs&&... H) const {
-#ifdef NO_BOOST_CPP17
-    // A check to ensure all arguments passed are all either matrices or are all pointers to matrices
-    constexpr bool are_all_mat = (... && (std::is_same<Matrix, std::decay_t<OptionalJacArgs>>::value));
-    constexpr bool are_all_ptrs = (... && (std::is_same<OptionalMatrixType, std::decay_t<OptionalJacArgs>>::value ||
-                                           std::is_same<OptionalNoneType, std::decay_t<OptionalJacArgs>>::value));
-    static_assert((are_all_mat || are_all_ptrs),
-                  "Arguments that are passed to the evaluateError function can only be of following the types: Matrix, "
-                  "or Matrix*");
-    // if they pass all matrices then we want to pass their pointers instead
-    if constexpr (are_all_mat) {
-      return evaluateError(x..., (&H)...);
-    } else {
-      return evaluateError(x..., std::forward<OptionalJacArgs>(H)..., static_cast<OptionalMatrixType>(OptionalNone));
-    }
-#else
-    // A check to ensure all arguments passed are all either matrices or are optionals of matrix references
-    constexpr bool are_all_mat = (... && (std::is_same<Matrix&, OptionalJacArgs>::value ||
-                                          std::is_same<OptionalMatrixType, std::decay_t<OptionalJacArgs>>::value ||
-                                          std::is_same<OptionalNoneType, std::decay_t<OptionalJacArgs>>::value));
-    static_assert(
-        are_all_mat,
-        "Arguments that are passed to the evaluateError function can only be of following the types: Matrix&, "
-        "boost::optional<Matrix&>, or boost::none_t");
-    return evaluateError(x..., std::forward<OptionalJacArgs>(H)..., OptionalNone);
-#endif
-  }
-};
-
 /**
  * Factor that supports arbitrary expressions via AD.
  *
@@ -398,14 +307,14 @@ struct traits<ExpressionFactorN<T, Args...>>
  * @deprecated Prefer the more general ExpressionFactorN<>.
  */
 template <typename T, typename A1, typename A2>
-class GTSAM_DEPRECATED ExpressionFactor2 : public ExpressionFactorN<T, A1, A2>, public EvaluateErrorInterface<A1, A2> {
+class GTSAM_DEPRECATED ExpressionFactor2 : public ExpressionFactorN<T, A1, A2> {
 public:
   /// Destructor
   ~ExpressionFactor2() override {}
 
   /// Backwards compatible evaluateError, to make existing tests compile
-  virtual Vector evaluateError(const A1& a1, const A2& a2, OptionalMatrixType H1,
-                               OptionalMatrixType H2) const override {
+  Vector evaluateError(const A1& a1, const A2& a2, OptionalMatrixType H1 = OptionalNone,
+                               OptionalMatrixType H2 = OptionalNone) const {
     Values values;
     values.insert(this->keys_[0], a1);
     values.insert(this->keys_[1], a2);
@@ -416,6 +325,7 @@ public:
     return error;
   }
 
+
   /// Recreate expression from given keys_ and measured_, used in load
   /// Needed to deserialize a derived factor
   virtual Expression<T> expression(Key key1, Key key2) const {
diff --git a/gtsam/nonlinear/NonlinearFactor.h b/gtsam/nonlinear/NonlinearFactor.h
index 398bc833d..be1fbb889 100644
--- a/gtsam/nonlinear/NonlinearFactor.h
+++ b/gtsam/nonlinear/NonlinearFactor.h
@@ -33,11 +33,7 @@
 namespace gtsam {
 
 /* ************************************************************************* */
-/*
- * Some typedef based aliases to compile these interfaces without boost if
- * the NO_BOOST_C17 flag is enabled
- */
-#ifdef NO_BOOST_CPP17
+
 // These typedefs and aliases will help with making the evaluateError interface
 // independent of boost
 using OptionalNoneType = std::nullptr_t;
@@ -52,16 +48,7 @@ using OptionalMatrixType = Matrix*;
 // independent of boost
 using OptionalMatrixVecType = std::vector<Matrix>*;
 #define OptionalMatrixVecNone static_cast<std::vector<Matrix>*>(nullptr)
-#else
-// creating a none value to use when declaring our interfaces
-using OptionalNoneType = boost::none_t;
-#define OptionalNone boost::none
-template <typename T = void>
-using OptionalMatrixTypeT = boost::optional<Matrix&>;
-using OptionalMatrixType = boost::optional<Matrix&>;
-using OptionalMatrixVecType = boost::optional<std::vector<Matrix>&>;
-#define OptionalMatrixVecNone boost::none
-#endif
+
 /**
  * Nonlinear factor base class
  *
@@ -258,12 +245,12 @@ public:
    * both the function evaluation and its derivative(s) in H.
    */
   virtual Vector unwhitenedError(const Values& x, OptionalMatrixVecType H = OptionalMatrixVecNone) const = 0;
-#ifdef NO_BOOST_CPP17
+
   // support taking in the actual vector instead of the pointer as well
   Vector unwhitenedError(const Values& x, std::vector<Matrix>& H) const {
 	  return unwhitenedError(x, &H);
   }
-#endif
+
   /**
    * Vector of errors, whitened
    * This is the raw error, i.e., i.e. \f$ (h(x)-z)/\sigma \f$ in case of a Gaussian
@@ -606,13 +593,11 @@ protected:
   virtual Vector evaluateError(const ValueTypes&... x,
                                OptionalMatrixTypeT<ValueTypes>... H) const = 0;
 
-#ifdef NO_BOOST_CPP17
   // if someone uses the evaluateError function by supplying all the optional
   // arguments then redirect the call to the one which takes pointers
   Vector evaluateError(const ValueTypes&... x, MatrixTypeT<ValueTypes>&... H) const {
 	  return evaluateError(x..., (&H)...);
   }
-#endif
 
   /// @}
   /// @name Convenience method overloads
@@ -634,7 +619,6 @@ protected:
    */
   template <typename... OptionalJacArgs, typename = IndexIsValid<sizeof...(OptionalJacArgs) + 1>>
   inline Vector evaluateError(const ValueTypes&... x, OptionalJacArgs&&... H) const {
-#ifdef NO_BOOST_CPP17
 	// A check to ensure all arguments passed are all either matrices or are all pointers to matrices
     constexpr bool are_all_mat = (... && (std::is_same<Matrix, std::decay_t<OptionalJacArgs>>::value));
     constexpr bool are_all_ptrs = (... && (std::is_same<OptionalMatrixType, std::decay_t<OptionalJacArgs>>::value ||
@@ -648,16 +632,6 @@ protected:
 	} else {
     return evaluateError(x..., std::forward<OptionalJacArgs>(H)..., static_cast<OptionalMatrixType>(OptionalNone));
 	}
-#else
-	// A check to ensure all arguments passed are all either matrices or are optionals of matrix references
-    constexpr bool are_all_mat = (... && (std::is_same<Matrix&, OptionalJacArgs>::value ||
-                                          std::is_same<OptionalMatrixType, std::decay_t<OptionalJacArgs>>::value ||
-                                          std::is_same<OptionalNoneType, std::decay_t<OptionalJacArgs>>::value));
-    static_assert(are_all_mat,
-                  "Arguments that are passed to the evaluateError function can only be of following the types: Matrix&, "
-                  "boost::optional<Matrix&>, or boost::none_t");
-    return evaluateError(x..., std::forward<OptionalJacArgs>(H)..., OptionalNone);
-#endif
   }
 
   /// @}
diff --git a/gtsam/sam/BearingFactor.h b/gtsam/sam/BearingFactor.h
index 242c9b258..670e25d84 100644
--- a/gtsam/sam/BearingFactor.h
+++ b/gtsam/sam/BearingFactor.h
@@ -34,10 +34,9 @@ struct Bearing;
  */
 template <typename A1, typename A2,
           typename T = typename Bearing<A1, A2>::result_type>
-struct BearingFactor : public ExpressionFactorN<T, A1, A2>, public EvaluateErrorInterface<A1, A2>{
+struct BearingFactor : public ExpressionFactorN<T, A1, A2> {
   typedef ExpressionFactorN<T, A1, A2> Base;
 
-  using EvaluateErrorInterface<A1,A2>::evaluateError;
   /// default constructor
   BearingFactor() {}
 
@@ -62,9 +61,8 @@ struct BearingFactor : public ExpressionFactorN<T, A1, A2>, public EvaluateError
     Base::print(s, kf);
   }
   
-  virtual Vector evaluateError(const A1& a1, const A2& a2,
-    OptionalMatrixType H1, OptionalMatrixType H2) const override
-  {
+  Vector evaluateError(const A1& a1, const A2& a2,
+    OptionalMatrixType H1 = OptionalNone, OptionalMatrixType H2 = OptionalNone) const {
     std::vector<Matrix> Hs(2);
     const auto &keys = Factor::keys();
     const Vector error = this->unwhitenedError(
diff --git a/gtsam/sam/BearingRangeFactor.h b/gtsam/sam/BearingRangeFactor.h
index bdd0888fb..4f3a38eac 100644
--- a/gtsam/sam/BearingRangeFactor.h
+++ b/gtsam/sam/BearingRangeFactor.h
@@ -33,7 +33,7 @@ template <typename A1, typename A2,
           typename B = typename Bearing<A1, A2>::result_type,
           typename R = typename Range<A1, A2>::result_type>
 class BearingRangeFactor
-    : public ExpressionFactorN<BearingRange<A1, A2>, A1, A2>, public EvaluateErrorInterface<A1, A2>{
+    : public ExpressionFactorN<BearingRange<A1, A2>, A1, A2> {
  private:
   typedef BearingRange<A1, A2> T;
   typedef ExpressionFactorN<T, A1, A2> Base;
@@ -41,7 +41,6 @@ class BearingRangeFactor
 
  public:
   typedef boost::shared_ptr<This> shared_ptr;
-  using EvaluateErrorInterface<A1, A2>::evaluateError;
 
   /// Default constructor
   BearingRangeFactor() {}
@@ -74,9 +73,8 @@ class BearingRangeFactor
                          Expression<A2>(keys[1]));
   }
 
-  virtual Vector evaluateError(const A1& a1, const A2& a2,
-      OptionalMatrixType H1, OptionalMatrixType H2) const override
-  {
+  Vector evaluateError(const A1& a1, const A2& a2,
+      OptionalMatrixType H1 = OptionalNone, OptionalMatrixType H2 = OptionalNone) const {
     std::vector<Matrix> Hs(2);
     const auto &keys = Factor::keys();
     const Vector error = this->unwhitenedError(
diff --git a/gtsam/sam/RangeFactor.h b/gtsam/sam/RangeFactor.h
index d5fb93179..e28dd5a5d 100644
--- a/gtsam/sam/RangeFactor.h
+++ b/gtsam/sam/RangeFactor.h
@@ -32,13 +32,12 @@ struct Range;
  * @ingroup sam
  */
 template <typename A1, typename A2 = A1, typename T = double>
-class RangeFactor : public ExpressionFactorN<T, A1, A2> , public EvaluateErrorInterface<A1, A2>{
+class RangeFactor : public ExpressionFactorN<T, A1, A2> {
  private:
   typedef RangeFactor<A1, A2> This;
   typedef ExpressionFactorN<T, A1, A2> Base;
 
  public:
-  using EvaluateErrorInterface<A1,A2>::evaluateError;
   /// default constructor
   RangeFactor() {}
 
@@ -60,8 +59,8 @@ class RangeFactor : public ExpressionFactorN<T, A1, A2> , public EvaluateErrorIn
     return Expression<T>(Range<A1, A2>(), a1_, a2_);
   }
 
-  virtual Vector evaluateError(const A1& a1, const A2& a2, OptionalMatrixType H1,
-                               OptionalMatrixType H2) const override {
+  Vector evaluateError(const A1& a1, const A2& a2, OptionalMatrixType H1 = OptionalNone,
+                               OptionalMatrixType H2 = OptionalNone) const {
     std::vector<Matrix> Hs(2);
     const auto& keys = Factor::keys();
     const Vector error = Base::unwhitenedError({{keys[0], genericValue(a1)}, {keys[1], genericValue(a2)}}, Hs);
@@ -97,7 +96,7 @@ struct traits<RangeFactor<A1, A2, T> >
  */
 template <typename A1, typename A2 = A1,
           typename T = typename Range<A1, A2>::result_type>
-class RangeFactorWithTransform : public ExpressionFactorN<T, A1, A2> , public EvaluateErrorInterface<A1, A2>{
+class RangeFactorWithTransform : public ExpressionFactorN<T, A1, A2> {
  private:
   typedef RangeFactorWithTransform<A1, A2> This;
   typedef ExpressionFactorN<T, A1, A2> Base;
@@ -105,7 +104,6 @@ class RangeFactorWithTransform : public ExpressionFactorN<T, A1, A2> , public Ev
   A1 body_T_sensor_;  ///< The pose of the sensor in the body frame
 
  public:
-  using EvaluateErrorInterface<A1, A2>::evaluateError;
   //// Default constructor
   RangeFactorWithTransform() {}
 
@@ -134,9 +132,8 @@ class RangeFactorWithTransform : public ExpressionFactorN<T, A1, A2> , public Ev
     return Expression<T>(Range<A1, A2>(), nav_T_sensor_, a2_);
   }
 
-  virtual Vector evaluateError(const A1& a1, const A2& a2,
-      OptionalMatrixType H1, OptionalMatrixType H2) const override
-  {
+  Vector evaluateError(const A1& a1, const A2& a2,
+      OptionalMatrixType H1 = OptionalNone, OptionalMatrixType H2 = OptionalNone) const {
     std::vector<Matrix> Hs(2);
     const auto &keys = Factor::keys();
     const Vector error = Base::unwhitenedError(
@@ -147,6 +144,12 @@ class RangeFactorWithTransform : public ExpressionFactorN<T, A1, A2> , public Ev
     return error;
   }
 
+  // An evaluateError overload to accept matrices (Matrix&) and pass it to the
+  // OptionalMatrixType evaluateError overload
+  Vector evaluateError(const A1& a1, const A2& a2, Matrix& H1, Matrix& H2) const {
+	return evaluateError(a1, a2, &H1, &H2);
+  }
+
   /** print contents */
   void print(const std::string& s = "",
              const KeyFormatter& keyFormatter = DefaultKeyFormatter) const override {
diff --git a/gtsam/sam/tests/testRangeFactor.cpp b/gtsam/sam/tests/testRangeFactor.cpp
index 200e1236a..6a71cbd2c 100644
--- a/gtsam/sam/tests/testRangeFactor.cpp
+++ b/gtsam/sam/tests/testRangeFactor.cpp
@@ -214,7 +214,7 @@ TEST( RangeFactor, Jacobian2D ) {
 
   // Use the factor to calculate the Jacobians
   Matrix H1Actual, H2Actual;
-  factor.evaluateError(pose, point, H1Actual, H2Actual);
+  factor.evaluateError(pose, point, &H1Actual, &H2Actual);
 
   // Use numerical derivatives to calculate the Jacobians
   Matrix H1Expected, H2Expected;
diff --git a/gtsam/slam/EssentialMatrixFactor.h b/gtsam/slam/EssentialMatrixFactor.h
index 7f3875d06..3e4a55dd6 100644
--- a/gtsam/slam/EssentialMatrixFactor.h
+++ b/gtsam/slam/EssentialMatrixFactor.h
@@ -295,15 +295,11 @@ class EssentialMatrixFactor3 : public EssentialMatrixFactor2 {
       // Version with derivatives
       Matrix D_e_cameraE, D_cameraE_E;  // 2*5, 5*5
       EssentialMatrix cameraE = E.rotate(cRb_, D_cameraE_E);
-#ifdef NO_BOOST_CPP17
 	  // Had to do this since the only overloaded function EssentialMatrixFactor2
 	  // uses the type OptionalMatrixType. Which would be a pointer when we are
 	  // not using boost. There is no way to redirect that call to the top (NoiseModelFactorN)
 	  // dereference it and bring it back to the Base (EssentialMatrixFactor2)
       Vector e = Base::evaluateError(cameraE, d, &D_e_cameraE, Dd);
-#else
-      Vector e = Base::evaluateError(cameraE, d, D_e_cameraE, Dd);
-#endif
       *DE = D_e_cameraE * D_cameraE_E;  // (2*5) * (5*5)
       return e;
     }
diff --git a/gtsam_unstable/slam/BetweenFactorEM.h b/gtsam_unstable/slam/BetweenFactorEM.h
index 871dd3eee..510011ede 100644
--- a/gtsam_unstable/slam/BetweenFactorEM.h
+++ b/gtsam_unstable/slam/BetweenFactorEM.h
@@ -228,11 +228,9 @@ public:
     return err_wh_eq;
   }
 
-#ifdef NO_BOOST_CPP17
   Vector whitenedError(const Values& x, std::vector<Matrix>& H) const {
 	  return whitenedError(x, &H);
   }
-#endif
 
   /* ************************************************************************* */
   Vector calcIndicatorProb(const Values& x) const {
diff --git a/gtsam_unstable/slam/TransformBtwRobotsUnaryFactor.h b/gtsam_unstable/slam/TransformBtwRobotsUnaryFactor.h
index 6d1ca832c..1a535eab6 100644
--- a/gtsam_unstable/slam/TransformBtwRobotsUnaryFactor.h
+++ b/gtsam_unstable/slam/TransformBtwRobotsUnaryFactor.h
@@ -186,11 +186,9 @@ namespace gtsam {
     }
 
     /* ************************************************************************* */
-#ifdef NO_BOOST_CPP17
     gtsam::Vector whitenedError(const gtsam::Values& x, std::vector<Matrix>& H) const {
 	  return whitenedError(x, &H);
     }
-#endif
 
 
     /* ************************************************************************* */
diff --git a/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h b/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h
index 52ff220e1..591a50f13 100644
--- a/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h
+++ b/gtsam_unstable/slam/TransformBtwRobotsUnaryFactorEM.h
@@ -245,11 +245,9 @@ namespace gtsam {
     }
     
     /* ************************************************************************* */
-#ifdef NO_BOOST_CPP17
 	Vector whitenedError(const Values& x, std::vector<Matrix>& H) const {
 	  return whitenedError(x, &H);
 	}
-#endif
 
     /* ************************************************************************* */
     Vector calcIndicatorProb(const Values& x) const {
diff --git a/tests/simulated3D.h b/tests/simulated3D.h
index 54481fcbb..8926b376a 100644
--- a/tests/simulated3D.h
+++ b/tests/simulated3D.h
@@ -99,12 +99,8 @@ struct PointPrior3D: public NoiseModelFactor1<Point3> {
 /**
  * Models a linear 3D measurement between 3D points
  */
-<<<<<<< HEAD
 struct Simulated3DMeasurement: public NoiseModelFactorN<Point3, Point3> {
-=======
-struct Simulated3DMeasurement: public NoiseModelFactor2<Point3, Point3> {
   using NoiseModelFactor2<Point3, Point3>::evaluateError;
->>>>>>> 7b3c40e92 (everything compiles but tests fail in no boost mode)
 
   Point3 measured_; ///< Linear displacement between a pose and landmark